Circulating stream opening method for chemical process simulation

Abstract

The invention discloses a circulating stream break-through method for chemical process simulation. The method comprises the following steps: determining upstream and downstream deviation variables and corresponding upstream and downstream variables; getting through and solving when the absolute connectivity is 0, and recording the variable value of the stream after success; in the relative adjustment stage, the temporary allowable change rate is preset, and the relative connectivity is calculated in combination with variable values; performing break-through solution of stage division according to the relative connectivity; if successful, entering an absolute adjustment stage and recording a corresponding variable value, otherwise, returning to a relative adjustment stage; in the absolute adjustment stage, the temporary allowable change rate is corrected, and the absolute connectivity is calculated in combination with a variable value obtained after previous successful break-through solving; performing break-through solution; and repeating the process of the absolute adjustment stage until the absolute connectivity is 1. According to the method, besides pressure deviation, a physical item with a breadth property is selected as an upstream and downstream deviation variable, and the same connectivity is given during break-through, so that the break-through success rate and stability of the circulating stream are improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical simulation, and in particular to a circulating flow stream opening method for chemical process simulation. Background Art

[0002] The circulation stream connection method of traditional steady-state process simulation software is based on the "sequential module method": first select several circulation streams as the connection objects, then assign initial values ​​to the downstream variables of these circulation streams, and solve the entire process flow according to the "sequential module method" to obtain the upstream variable results of these circulation streams. If their upstream and downstream deviation variables are within the allowable tolerance range, it is considered that the connection is successful. If they are not within the allowable tolerance range, it is necessary to update the downstream variable values ​​(iteration values) of these circulation streams according to a certain connection algorithm, and perform the next solution... and so on. Each time the downstream variable values ​​(iteration values) of these circulation streams are updated according to a certain connection algorithm, the correlation between these variables is often not considered. Since the "sequential module method" is used, each unit module is calculated one by one instead of at the same time each time the solution is solved, so the solution efficiency is low.

[0003] The “method for opening up circulating streams in process simulation” disclosed in the Chinese patent literature has a publication number of CN117473905A and a publication date of 2024.01.30, and includes: S1, obtaining the initial value of the stream of the feed and the initial value of the circulating stream; S2. Based on the initial value of the feed stream and the initial value of the circulating stream, the deviation value of all streams is obtained; S3. The connectivity is received, and the deviation value of the stream is used as the deviation value of the previous round, and based on the connectivity and the deviation value from the previous round, the deviation value of this round and the connection equation of this round are obtained; S4. The connection equation of this round and the first set of equations are combined to obtain the combined equations and solved. If the convergence condition is met, the new connectivity is received, and the deviation value of this round is used as the new deviation value of the previous round, and based on the new connectivity and the new deviation value of the previous round, the new deviation value of this round and the connection equation of this round are obtained; if not met, the new connectivity is received, and based on the new connectivity and the deviation value of the previous round, the new deviation value of this round and the connection equation of this round are obtained; S5. Repeat S4-S5 until the new deviation value of this round is 0. Although this technology solves the problems existing in the sequential module method, it does not provide a method for selecting the deviation value variable and adjusting the connectivity of the flow stream when opening up. If the deviation value variable is not selected reasonably and the connectivity adjustment setting is not reasonable during the cyclic iteration process, it is easy to cause the solution to fail and the flow to be opened up, which will seriously affect the success rate and stability of the circulation flow. Summary of the invention

[0004] The present invention aims to overcome the problem in the prior art that when opening up circulating streams, if the deviation value variable selection is unreasonable and the adjustment setting of the connectivity during the cyclic iteration is unreasonable, it is easy to cause the solution to fail and the opening up cannot be performed, thereby seriously affecting the success rate and stability of the opening up of the circulating streams. A circulating stream opening up method for chemical process simulation is provided to overcome the problem in the prior art that when opening up circulating streams, if the deviation value variable selection is unreasonable and the adjustment setting of the connectivity during the cyclic iteration is unreasonable, it is easy to cause the solution to fail and the opening up cannot be performed, thereby seriously affecting the success rate and stability of the opening up of the circulating streams.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A circulating stream opening method for chemical process simulation, comprising: Determine upstream and downstream deviation variables and upstream and downstream variables; When the absolute connectivity is 0, solve the problem and record the variable value of the successful stream. In the relative adjustment phase, a temporary allowable change rate is preset and the relative connectivity is calculated in combination with the variable values; Solving the problem by dividing the stages according to the relative connectivity; If successful, it enters the absolute adjustment stage and records the variable values ​​of the stream, otherwise it returns to the relative adjustment stage; In the absolute adjustment stage, the temporary allowable change rate is corrected, and the absolute connectivity is calculated based on the variable values ​​after the previous successful connection solution; the connection solution is performed; The absolute adjustment phase is repeated until the absolute connectivity is 1.

[0006] The present invention is a technical improvement based on the existing process simulation circulating flow stock opening method. In addition to the pressure deviation, physical items of breadth properties are selected as upstream and downstream deviation variables, such as enthalpy flow deviation, component flow deviation, total flow deviation, etc., and all upstream and downstream deviation variables are given the same connectivity when the connectivity is adjusted, so that the upstream and downstream deviation variables are gradually reduced in the same proportion, thereby improving the opening success rate and stability of the circulating flow; at the same time, a method for adjusting the connectivity during the cyclic iterative opening process is provided, and the results of the connectivity parameters in each opening process are calculated, which not only improves the speed of the connectivity adjustment during the opening process of the circulating flow, but also ensures the success rate of the opening of the circulating flow.

[0007] Preferably, the upstream and downstream deviation variables are at least two of the pressure deviation in the circulating stream and the deviation of the physical item of the extensive property in the circulating stream; The upstream and downstream variables are a combination of variables corresponding to the upstream and downstream deviation variables.

[0008] Preferably, in the relative adjustment stage, a temporary allowable change rate is preset, and the relative connectivity is calculated in combination with the variable value; if the relative connectivity is greater than 1, a connection is solved with an absolute connectivity of 1; if the solution is successful, the connection is completed; if the solution is unsuccessful, or the connection solution divided by the stage is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition, and the relative connectivity is recalculated; Otherwise, the absolute connectivity is calculated based on the relative connectivity, and the solution is solved by dividing the stages.

[0009] Preferably, the calculating of the relative connectivity comprises: obtaining the variable value of the stream after the last successful solution; For any downstream variable, the relative connectivity of the variable is obtained by multiplying the value of the variable by the temporary allowable change rate of the variable and dividing it by the value of the upstream and downstream deviation variable corresponding to the variable. Traverse the relative connectivity of all variables and select the smallest one as the final relative connectivity.

[0010] Preferably, in the absolute adjustment stage, the temporary allowable change rate is corrected according to the second preset condition, and the absolute connectivity is calculated in combination with the variable value after the previous successful connection solution; If the absolute connectivity is greater than 1, the solution is solved with the absolute connectivity of 1; If the solution is successful, the connection is completed; If the solution is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition and the absolute connectivity is recalculated.

[0011] Preferably, in the absolute adjustment stage, if the absolute connectivity is less than or equal to 1, the absolute connectivity is converted into relative connectivity, and a connection solution is performed; If the solution is successful, the variable value of the stream after the success is recorded, and after the temporary allowable change rate is corrected according to the second preset condition, the absolute connectivity is recalculated in combination with the latest recorded variable value; If the solution is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition and the absolute connectivity is recalculated.

[0012] Preferably, the calculating of the absolute connectivity comprises: obtaining the variable value of the stream after the last successful solution; For any variable, calculate the absolute connectivity corresponding to the variable’s change rate after the next solution is equal to the temporary allowable change rate of the variable; Traverse all variables and select the smallest one as the final absolute connectivity.

[0013] Preferably, in the relative adjustment stage, the temporary allowable change rate of any downstream variable is numerically equal to the reference allowable change rate of the variable, and takes a positive sign when the downstream variable value is less than or equal to the corresponding upstream variable value, otherwise takes a negative sign.

[0014] Preferably, the first preset condition includes: The previous temporary permissible change rate shall be halved to become the new temporary permissible change rate; Determine whether the new temporary allowed change rate is greater than or equal to the preset minimum allowed change rate. If so, the temporary allowed change rate is corrected; otherwise, the connection fails.

[0015] Preferably, in the absolute adjustment stage, the second preset condition includes: obtaining the variable value of the stream after the last successful solution; For any variable, the maximum value between the reference allowable change rate of the variable and the actual change rate of the variable after the last successful solution is selected as the temporary allowable change rate of the variable. When the downstream variable value corresponding to the variable is less than or equal to the corresponding upstream variable value, the positive sign is taken, otherwise the negative sign is taken.

[0016] The present invention has the following beneficial effects: in addition to the pressure deviation, physical items of breadth properties are selected as upstream and downstream deviation variables, such as enthalpy flow deviation, component flow deviation, total flow deviation, etc., and all upstream and downstream deviation variables are given the same connectivity when the connectivity is adjusted, so that the upstream and downstream deviation variables are gradually reduced in the same proportion, thereby improving the success rate and stability of the circulation flow opening; a method for adjusting the connectivity in the process of cyclic iterative opening is disclosed, and a method for obtaining the connectivity parameters in each opening process is provided, which not only improves the speed of the connectivity adjustment in the circulation flow opening process, but also ensures the success rate of the circulation flow opening. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the circulating stream opening method of chemical process simulation in the present invention.

[0018] Figure 2 It is a schematic diagram of the upstream and downstream deviation variable selection in the present invention.

[0019] Figure 3 Schematic diagram of the circulating stream in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0021] In the prior art, the process of opening up the circulation flow stocks by the simultaneous equation method includes setting the circulation flow stocks to be opened up to "empty connection" first. At this time, the downstream variables will be used as known variables, and the downstream variables and upstream and downstream deviation variables will be used as unknown variables. Then, these downstream variables are assigned initial values, and global solutions are performed to obtain the values ​​of the downstream variables and upstream and downstream deviation variables. Then, it is switched to "real connection". At this time, the upstream and downstream deviation variables will be used as known variables, and the downstream variables and upstream variables will be used as unknown variables. These upstream and downstream deviation variables are reduced by adjusting the relative connectivity, and then the solution is performed according to the simultaneous equation method. After the solution is successful, these upstream and downstream deviation variables are further reduced by adjusting the relative connectivity... and so on, until these upstream and downstream deviation variables are reduced to 0, that is, the opening is successful. This method solves the shortcomings of the traditional circulation flow stock opening method based on the sequential module method, and can ensure that the values ​​of the upstream and downstream deviation variables are smaller than the previous time after each successful solution, and each unit module is calculated simultaneously during each solution, so the solution efficiency is high.

[0022] However, in the process of adjusting the relative connectivity, or in other words, reducing these upstream and downstream deviation variables, not all upstream and downstream deviation variables can be adjusted at will (especially when the initial value quality of the stream is poor), otherwise it is easy to cause the equation system to have no solution, resulting in failure to solve the next time, that is, failure to connect. At the same time, in the process of adjusting the connectivity (that is, reducing the upstream and downstream deviation variables), the amplitude of each adjustment is difficult to control: if it is adjusted too small, it will lead to too long a time to connect, and if it is adjusted too large, it will easily lead to failure to solve.

[0023] In order to solve the above problems, the present invention provides Figure 1 A circulating stream opening method for a chemical process simulation shown in the figure includes: Determine several upstream and downstream deviation variables and corresponding upstream and downstream variables for opening up the circulation stream; When the absolute connectivity is 0, solve the problem and record the variable values ​​of the flow stream after success; In the relative adjustment phase, a temporary allowable change rate is preset, and the relative connectivity is calculated in combination with the variable values; Calculate the absolute connectivity based on the relative connectivity and solve the problem by dividing the stages; If successful, it enters the absolute adjustment phase and records the corresponding variable values, otherwise it returns to the relative adjustment phase; In the absolute adjustment stage, the temporary allowable change rate is corrected, and the absolute connectivity is calculated in combination with the variable values ​​after the previous successful connection solution; the connection solution is performed; The process of the absolute adjustment phase is repeated until the absolute connectivity is 1.

[0024] It should be noted that the present invention is a technical improvement based on the existing process simulation circulating flow stock opening method. In addition to the pressure deviation, physical items of breadth properties are selected as upstream and downstream deviation variables, such as enthalpy flow deviation, component flow deviation, total flow deviation, etc., and all upstream and downstream deviation variables are given the same connectivity when the connectivity is adjusted, so that the upstream and downstream deviation variables are gradually adjusted down in the same proportion, thereby improving the opening success rate and stability of the circulating flow; at the same time, a method for adjusting the connectivity during the cyclic iterative opening process is provided, and the results of the connectivity parameters in each opening process are calculated, which not only improves the speed of the connectivity adjustment during the opening process of the circulating flow, but also ensures the success rate of the opening of the circulating flow.

[0025] It is worth noting that the present invention is the same as the prior art, and is also based on the simultaneous equation method, through "empty connection", "real connection" and adjustment of the degree of connection to open up the circulating flow stream. Therefore, the technical content disclosed in the patent can be regarded as the known prior art of the present invention and no longer described in detail (that is, the method of the present invention no longer describes the calculation process of the initial empty connection stage in the opening process, and starts from the real connection part), but the difference is that the present invention provides specific technical features, that is, which physical items should be selected as upstream and downstream deviation variables and the corresponding method of how to adjust the upstream and downstream deviation variable values. Compared with the prior art, the success rate and stability of the solution of the method of the present invention will be greatly improved in the process of adjusting the relative degree of connection.

[0026] Specifically, stream: used to describe the material connection relationship between each unit module in the chemical process flow. The upstream variables of the stream and the downstream variables of the stream: the upstream variables of the stream are all or part of the export variables of the upstream unit module, and the downstream variables of the stream are all or part of the import variables of the downstream unit module. The upstream variables of the stream and the downstream variables of the stream must correspond one to one. For example, when the upstream variables of the stream are "pressure, specific enthalpy, fraction of each component, total flow", the downstream variables of the stream must also be "pressure, specific enthalpy, fraction of each component, total flow".

[0027] When some inlet variables of the downstream unit module are used as downstream variables of the stream, other inlet variables of the downstream unit module need to be obtained through "flash calculation" etc. For example, all the inlet variables of the downstream unit module are "pressure, temperature, specific enthalpy, fraction of each component, total flow, molar mass, molar volume", and only "pressure, specific enthalpy, fraction of each component, total flow" are selected as downstream variables of the stream, then other inlet variables of the downstream unit module ("temperature, molar mass, molar volume") need to be obtained through flash calculation etc., that is, "temperature, molar mass, molar volume" are calculated according to "pressure, specific enthalpy, fraction of each component, total flow" transmitted by the stream.

[0028] Stream upstream and downstream deviation variable: the difference between the downstream and upstream of a physical item (such as temperature, enthalpy flow, etc.). When the stream upstream and downstream variables contain this physical item, then the stream upstream and downstream deviation variable = the value of the stream downstream variable - the value of the stream upstream variable. For example: the stream upstream and downstream variables contain "temperature", then: temperature deviation = stream downstream temperature - stream upstream temperature. When the stream upstream and downstream variables do not contain this physical item, for example: the stream upstream and downstream variables contain "total flow and specific enthalpy" but no "enthalpy flow", then enthalpy flow deviation = stream downstream specific enthalpy * stream downstream total flow - stream upstream specific enthalpy * stream upstream total flow.

[0029] Circulating stream: In the chemical process, the connection relationship between materials often forms a "loop". The streams in a loop are called circulating streams. Stream connection equation: used to describe the mathematical relationship between the upstream variables of the stream, the downstream variables of the stream, and the upstream and downstream deviation variables of the stream.

[0030] Empty connection: When a stream is in an empty connection state, the downstream variables of the stream will be used as known variables, and the upstream variables and upstream and downstream deviation variables will be used as unknown variables. Real connection: When a stream is in a real connection state, the upstream and downstream deviation variables of the stream will be used as known variables, and the upstream variables and upstream variables will be used as unknown variables.

[0031] Connectivity: For the connected streams, the value of the upstream and downstream deviation variable can be changed by adjusting the connectivity. Relative connectivity: The upstream and downstream deviation variable value used when solving the current set of equations = the previous upstream and downstream deviation variable value * (1-relative connectivity). Absolute connectivity: The upstream and downstream deviation variable value used when solving the current set of equations = the initial upstream and downstream deviation variable value * (1-absolute connectivity). Since relative connectivity and absolute connectivity can be converted by calculation, the differences between relative connectivity, absolute connectivity and connectivity are not specifically distinguished in the subsequent specific embodiment description.

[0032] As a specific embodiment, the upstream and downstream deviation variables of the circulation stream opening are at least two of the pressure deviation and the deviation of the physical item of the extensive property in the circulation stream; The upstream and downstream variables are the variable combinations corresponding to the upstream and downstream deviation variables; When adjusting the upstream and downstream deviation variables by absolute connectivity or relative connectivity, all upstream and downstream deviation variables are adjusted in the same proportion, that is, the absolute connectivity (relative connectivity) of all streams is the same during each opening process.

[0033] It should be noted that the physical terms of extensive properties refer to properties that are numerically proportional to the amount of substance in the system and are additive, such as mass flow, molar flow, enthalpy flow, etc. The physical terms of intensive properties refer to properties that are numerically independent of the amount of substance in the system, and their values ​​depend on the characteristics of the system itself and are not additive, such as temperature, pressure, mass fraction, molar fraction, specific enthalpy, etc. Selecting at least two of the physical terms of extensive properties other than pressure deviation as upstream and downstream deviation variables, such as "enthalpy flow deviation, flow deviation of each component, total flow deviation", etc., and based on this, selecting the same relative connectivity for adjusting the upstream and downstream deviation variables can greatly improve the success rate and stability of the through-solution.

[0034] It is worth noting that if Figure 2 The figure shows a schematic diagram of the upstream and downstream deviation variable selection. Starting from the perspective of chemical industry, the present invention constructs a chemical process flow-NEW for the circulating streams to be opened up on the basis of the chemical process flow built based on the prior art, and this chemical process flow-NEW can reflect the process of opening up the circulating streams (the opening process of the pressure item cannot be reflected). Figure 2 The schematic diagram on the left is a schematic diagram of opening up the circulating flow stream according to the prior art CN117473905A and CN113050416B, which is a purely mathematical process and has no chemical significance.

[0035] The following describes the construction process of Chemical Process Flow-NEW according to the process of opening up the circulating flow stream, taking the circulating flow stream S1 as an example: Since Chemical Process Flow-NEW cannot reflect the opening process of the pressure item, it is assumed that the pressure item has been opened up.

[0036] First, we set the circulating stream S1 to an empty connection and assign initial values ​​to the downstream variables. Then we perform a global solution to obtain the values ​​of the downstream variables and the upstream and downstream deviation variables. Then we switch S1 to a real connection, set the connection degree to 0, and solve once. At this point, we can Figure 2 Based on the schematic diagram on the left, a mixer, a diverter, and a virtual material source are added to construct a chemical process flow - NEW: that is, the material in the virtual material source, after mixing with the material upstream of S1, is exactly equal to the material downstream of S1. Figure 2 As shown in the schematic diagram on the right.

[0037] Virtual material source, flow rate of component i: Fi_S1 downstream - Fi_S1 upstream = BIAS_Fi. Enthalpy flow rate: H_S1 downstream - H_S1 upstream = BIAS_H. Pressure: P_S1 downstream or P_S1 upstream (opened). Diverter: main side opening = 1 (bypass side opening = 0).

[0038] Therefore, according to the chemical process flow - NEW, the process of opening the circulating stream S1 (except the pressure term) is equivalent to: gradually increasing the bypass side opening of the diverter to 1 (main side opening = 1-bypass side opening). Mathematically, the above process is equivalent to: still following the process of the prior art, but requiring BIAS_Fi, BIAS_H, and BIAS_P to be selected as upstream and downstream deviation variables, and BIAS_Fi and BIAS_H to be reduced in the same proportion.

[0039] From the perspective of chemical operations, after each adjustment of the diverter opening, the chemical process flow - NEW is likely to have a steady-state condition, and the corresponding large nonlinear equation group is likely to have a solution. Therefore, selecting BIAS_Fi, BIAS_H, and BIAS_P as upstream and downstream deviation variables, and reducing BIAS_Fi and BIAS_H in the same proportion can greatly improve the success rate and stability of the solution in the process of opening up the circulating flow. That is, the deviation variables of at least two of the pressure deviation and the physical terms of the breadth property are selected as the upstream and downstream deviation variables, and the absolute connectivity (relative connectivity) of all flow streams is the same during each opening process. BIAS: Upstream and downstream deviation variables. P: Pressure. H: Enthalpy flow. Fi: Flow rate of component i.

[0040] Specifically, the following takes a circulating stream scenario involving only gas and liquid as an example to describe the selection of upstream and downstream deviation variables (and corresponding upstream variables, downstream variables, and connection equations).

[0041] There are two options for upstream and downstream deviation variables of the circulating stream: Option 1: pressure deviation, SI unit is Pa; enthalpy flow deviation, SI unit is J / s; flow deviation of each component (or flow deviation of component i), SI unit is kg / s or kmol / s.

[0042] Option 2: Pressure deviation, SI unit is Pa; enthalpy flow deviation, SI unit is J / s; total flow deviation, SI unit is kg / s or kmol / s. Flow deviation of each component (or flow deviation of component i), SI unit is kg / s or kmol / s.

[0043] Corresponding to the upstream and downstream deviation variables of the circulating stream, four combinations of upstream and downstream variables can be selected: When the upstream and downstream deviation variables adopt scheme 1: Combination method 1: pressure, specific enthalpy, flow rate of each component. Combination method 2: pressure, enthalpy flow, flow rate of each component.

[0044] When the upstream and downstream deviation variables adopt the scheme 2: Combination method 3: pressure, specific enthalpy, total flow rate, and the fraction of each component. Combination method 4: pressure, enthalpy flow rate, total flow rate, and the fraction of each component.

[0045] The connection equation of the circulating stream is: When the upstream and downstream variables are combined in mode 1: Pressure connection equation: upstream pressure - downstream pressure + pressure deviation = 0. Enthalpy connection equation: upstream specific enthalpy*∑ upstream component i flow rate - downstream specific enthalpy*∑ downstream component i flow rate + enthalpy flow rate deviation = 0. Component connection equation: upstream component i flow rate - downstream component i flow rate + component i flow rate deviation = 0.

[0046] When the upstream and downstream variables are combination mode 2: Pressure connection equation: upstream pressure - downstream pressure + pressure deviation = 0. Enthalpy connection equation: upstream enthalpy flow - downstream enthalpy flow + enthalpy flow deviation = 0. Component connection equation: flow of upstream component i - flow of downstream component i + flow deviation of component i = 0.

[0047] When the upstream and downstream variables are in combination mode 3: Pressure connection equation: upstream pressure - downstream pressure + pressure deviation = 0. Enthalpy connection equation: upstream specific enthalpy * upstream total flow - downstream specific enthalpy * downstream total flow + enthalpy flow deviation = 0. Total flow connection equation: upstream total flow - downstream total flow + total flow deviation = 0. Component connection equation: upstream component i fraction * upstream total flow - downstream component i fraction * downstream total flow + component i flow deviation = 0.

[0048] When the upstream and downstream variables are combination mode 4: Pressure connection equation: upstream pressure - downstream pressure + pressure deviation = 0. Enthalpy connection equation: upstream enthalpy flow - downstream enthalpy flow + enthalpy flow deviation = 0. Total flow connection equation: upstream total flow - downstream total flow + total flow deviation = 0. Component connection equation: (upstream component i fraction - downstream component i fraction) * total flow + component i flow deviation = 0.

[0049] The method of solving the circulation flow stream opening based on the selection of the upstream and downstream deviation variables mentioned above is explained. First, set the flow stream to be opened as an empty connection, and assign initial values ​​to the downstream variables, and then perform a global solution to obtain the values ​​of the upstream variables and the upstream and downstream deviation variables. Then switch the flow stream to be opened to a real connection, set the connection degree to 0, and solve once. Record the successful solution results: P / H / Fi in each phase of all affected flow streams.

[0050] Next, a reference allowable change rate is preset (e.g., 10%). That is, a change rate less than the reference allowable change rate is considered a small change rate. Then, the absolute connection degree is adjusted. The absolute connection degrees of all the streams to be connected are adjusted together, that is, they are all equal.

[0051] Then start adjusting the connectivity for the first time and perform a solution. Record the successful solution result: P / H / Fi in each phase of all affected streams. Calculate and record the actual change rate of P / H / Fi in each phase of all streams to be connected and all affected streams after the solution is successful (i.e., the numerical change of the variable before and after the solution is successful).

[0052] The basis for the adjustment range of the degree of connection is whether the rate of change of the working conditions of the downstream flow stream to be opened is small at the moment after the diverter opening is adjusted. That is, according to the reference allowable change rate, the rate of change of the working conditions of the downstream flow stream to be opened at the moment after the diverter opening is adjusted should be less than or equal to the reference allowable change rate, and the corresponding temporary allowable change rate is selected to calculate the corresponding absolute degree of connection.

[0053] Specifically, taking the hydrogen flow rate F_H2 as an example, F_H2_upstream = 8000 kg / hr, F_H2_downstream = 9000 kg / hr, BIAS_F_H2 = 1000 kg / hr. According to the reference allowable change rate, F_H2_downstream changes from 9000 to 9000*(1-10%) = 8100 kg / hr, so the corresponding BIAS_F_H2 will change from 1000 to 1000-900 = 100 kg / hr, that is, the absolute connectivity should be adjusted from 0 to (1-100 / 1000) = 0.9 (the bypass side opening of the diverter is adjusted from 0 to 0.9). Similarly, the absolute connectivity corresponding to other Fi and H can be calculated, and then the smallest absolute connectivity can be taken for subsequent opening and solving, so as to ensure that the change rate of the working conditions of the downstream of the flow stream is within an appropriate range at the moment after the diverter opening is adjusted. Actual change rate = successful result of this operation / successful result of the last operation - 1.

[0054] Then continue to adjust the connectivity, and perform a solution after each adjustment. Record the successful solution results: P / H / Fi in each phase of all affected streams. Calculate and record the actual change rate of P / H / Fi in each phase of all streams to be connected and all affected streams after the solution is successful.

[0055] The basis for the adjustment range of the connection degree is whether the change rate of the working conditions of all affected streams is small before and after the adjustment of the diverter opening. In fact, the change rate that P / H / Fi in each phase of each stream can withstand is different. Therefore, considering the efficiency of adjusting the connection degree, the temporary allowable change rate based on each adjustment will select the largest one from the actual change rate and the reference allowable change rate.

[0056] Since the solution has been successfully solved 2 times or more, the absolute connectivity corresponding to the change rate of the working condition of each affected stream can be estimated by linear extrapolation when the change rate is the temporary allowable change rate. Similarly, the P / H / Fi in each phase of all streams to be opened and all affected streams can calculate a corresponding absolute connectivity. The smallest absolute connectivity is taken as the absolute connectivity of all streams to be opened in this solution. Repeat the above steps until the opening solution is successful.

[0057] In the above process, if a solution fails, the change rate based on it will be temporarily allowed to be halved, and then the corresponding absolute connectivity will be recalculated and the solution will be attempted again.

[0058] As a specific embodiment, in the relative adjustment stage, a temporary allowable change rate is preset, and the relative connectivity is calculated in combination with the variable value; If the relative connectivity is greater than 1, the absolute connectivity is 1 for connection solving; if the solution is successful, the connection is completed; if the solution is unsuccessful, or the connection solution of the stage division is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition, and the relative connectivity is recalculated; Otherwise, the absolute connectivity is calculated based on the relative connectivity, and the solution is solved by dividing the stages.

[0059] Calculating the relative connectivity includes: obtaining the variable values ​​of the stream after the last successful solution; For any downstream variable, the relative connectivity of the variable is obtained by multiplying the value of the variable by the temporary allowable change rate of the variable and dividing it by the value of the upstream and downstream deviation variable corresponding to the variable. Traverse the relative connectivity of all variables and select the smallest one as the final relative connectivity.

[0060] In the relative adjustment stage, the temporary allowable change rate of any downstream variable is numerically equal to the reference allowable change rate of the variable. When the downstream variable value is less than or equal to the corresponding upstream variable value, it takes a positive sign, otherwise it takes a negative sign.

[0061] The first precondition includes: The previous temporary permissible change rate shall be halved to become the new temporary permissible change rate; Determine whether the new temporary allowed change rate is greater than or equal to the preset minimum allowed change rate. If so, the temporary allowed change rate is corrected; otherwise, the connection fails.

[0062] As a specific embodiment, in the absolute adjustment stage, the temporary allowable change rate is corrected according to the second preset condition, and the absolute connectivity is calculated in combination with the variable value after the previous successful connection solution; If the absolute connectivity is greater than 1, the solution is solved with the absolute connectivity of 1; If the solution is successful, the connection is completed; If the solution is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition and the absolute connectivity is recalculated.

[0063] In the absolute adjustment stage, if the absolute connectivity is less than or equal to 1, the absolute connectivity is converted into relative connectivity and the solution is performed; If the solution is successful, the variable value of the flow stream after the success is recorded, and after the temporary allowable change rate is corrected according to the second preset condition, the absolute connectivity is recalculated in combination with the latest recorded variable value; If the solution is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition and the absolute connectivity is recalculated.

[0064] Calculating the absolute connectivity includes: obtaining the variable values ​​of the stream after the last successful solution; For any variable, calculate the absolute connectivity corresponding to the variable’s change rate after the next solution is equal to the temporary allowable change rate of the variable; Traverse all variables and select the smallest one as the final absolute connectivity.

[0065] In the absolute adjustment stage, the second preset condition includes: obtaining the variable value of the stream after the last successful solution; For any variable, the maximum value between the reference allowable change rate of the variable and the actual change rate of the variable after the last successful solution is selected as the temporary allowable change rate of the variable. When the downstream variable value corresponding to the variable is less than or equal to the corresponding upstream variable value, the positive sign is taken, otherwise the negative sign is taken.

[0066] Specifically, the process of adjusting the degree of connection to open up the circulating stream is as follows.

[0067] Step A: Preset: Reference allowable change rate (must be a positive real number > 0), default is 10%. Minimum allowable change rate (must be a positive real number > 0), default is 1%. Lower limit of component flow (must be a positive real number > 0), default is 1E-10kg / s. Maximum allowable number of successful adjustments (must be a positive integer > 0), default is 50 times.

[0068] Step B: For the N flows to be connected, determine the flows that will be affected during the connection process based on upstream and downstream relationships, etc. Assume that there are NS affected flows (excluding the N flows to be connected).

[0069] Step C: Switch all the N streams to be connected to real connection; set the relative connection of the N streams to be connected to 0. At this time, the corresponding absolute connection is also 0. Solve the global simultaneous equations EO. Then determine whether the solution is successful. If successful, execute step D; if unsuccessful, exit to indicate that the connection has failed (automatic adjustment of the connection has failed).

[0070] Step D: Record the result of this successful solution, including: the absolute connectivity used in this solution; the P / H / Fi in each phase of the upstream and downstream of the N streams to be solved; the P / H / Fi in each phase of the upstream of the NS affected streams. Record: Number of successful adjustments = 0.

[0071] Step E: Assign the temporary allowable change rate of P / H / Fi of the downstream of the N streams to be opened respectively: Temporary allowable change rate_P = ±reference allowable change rate (+ sign is taken when upstream value ≥ downstream value, and - sign is taken when upstream value < downstream value); Temporary allowable change rate_H = ±reference allowable change rate (+ sign is taken when upstream value ≥ downstream value, and - sign is taken when upstream value < downstream value); Temporary allowable change rate_Fi = ±reference allowable change rate (+ sign is taken when upstream value ≥ downstream value, and - sign is taken when upstream value < downstream value).

[0072] Step F: For the N streams to be opened, calculate the corresponding relative connectivity according to their downstream P / H / Fi and temporary allowable change rate: Relative connectivity_P = -P*temporary allowable change rate_P / BIAS_P; Relative connectivity_H = ABS(H*temporary allowable change rate_H / BIAS_H); Relative connectivity_Fi = -Fi*temporary allowable change rate_Fi / BIAS_Fi. If BIAS = 0, the relative connectivity result is infinite. Take the smallest relative connectivity among the above calculation results and record it as relative connectivity -MIN. Then check whether it is less than or equal to 1; if so, execute step I; if not, execute step G.

[0073] Step G: Set the relative connectivity of the N streams to be connected to 1. At this time, the absolute connectivity is also 1. Solve the global simultaneous equations EO. Then determine whether the solution is successful; if successful, exit to indicate that the connection is successful (automatic adjustment of connectivity is successful); if unsuccessful, execute step H.

[0074] Step H: Modify the temporary allowable change rate of P / H / Fi of the downstream of the N streams to be connected: temporary allowable change rate = temporary allowable change rate / 2. Determine whether the modified temporary allowable change rate is greater than or equal to the minimum allowable change rate; if yes, return and execute step F; if not, exit to indicate that the connection has failed (automatic adjustment of the connection degree has failed).

[0075] Step I: Set the relative connectivity of the N streams to be connected to relative connectivity - MIN. Calculate the "absolute connectivity" at this time. Solve the global simultaneous equations EO. Then determine whether the solution is successful; if successful, execute step K; if unsuccessful, execute step J.

[0076] Step J: Modify the temporary allowable change rate of P / H / Fi of the downstream of the N streams to be connected: temporary allowable change rate = temporary allowable change rate / 2. Determine whether the modified temporary allowable change rate is greater than or equal to the minimum allowable change rate; if yes, return and execute step F; if not, exit to indicate that the connection has failed (automatic adjustment of the connection degree has failed).

[0077] Step K: Record the successful result of this opening, including: the absolute connectivity used in this opening; the P / H / Fi in each phase of the upstream and downstream of the N streams to be opened; the P / H / Fi in each phase of the upstream of the NS affected streams. Number of successful adjustments = number of successful adjustments + 1, and then determine whether it is less than the maximum allowed number of successful adjustments; if yes, execute step L; if not, exit to indicate that the opening has failed (automatic adjustment of connectivity has failed).

[0078] Step L: Start a new opening process, taking the data recorded in step K as the result of the last successful opening, calculate the actual change rate of P / H / Fi in each phase of the upstream and downstream of the N flow streams to be opened; calculate the actual change rate of P / H / Fi in each phase of the upstream of the NS affected flow streams.

[0079] Step M: Assign temporary allowable change rates of P / H / Fi to the downstream of the N to-be-opened streams and the NS affected streams respectively: Temporary allowable change rate_P = ±MAX(ABS(temporary allowable change rate_P),ABS(reference allowable change rate),ABS(actual change rate_P))(+ sign is used when upstream value ≥ downstream value, and - sign is used when upstream value < downstream value); Temporary allowable change rate_H = ±MAX(ABS(temporary allowable change rate_H),ABS(reference allowable change rate),ABS(actual change rate_H))(+ sign is used when upstream value ≥ downstream value, and - sign is used when upstream value < downstream value); Temporary allowable change rate_Fi=±MAX(ABS(temporary allowable change rate_Fi),ABS(reference allowable change rate),ABS(actual change rate_Fi))(+ sign is taken when upstream value ≥ downstream value, and - sign is taken when upstream value < downstream value).

[0080] It is worth noting that if the following conditions exist in a phase of the above stream, the corresponding temporary allowable change rate needs to be modified as follows: The last successful Fi is less than the lower limit of the component flow, but ∑Fi is greater than the sum of the lower limits of all component flows. Then: the temporary allowable change rate corresponding to the Fi less than the lower limit of the component flow_Fi = reference allowable change rate; If the last successful connection ∑Fi is less than or equal to the sum of the lower limits of all component flow rates, then: temporary allowable change rate_P = reference allowable change rate, temporary allowable change rate_H = reference allowable change rate, and temporary allowable change rate_Fi corresponding to all Fi = reference allowable change rate.

[0081] Step N: For the P / H / Fi and temporary allowable change rate of each phase of the N upstream and downstream of the N flow streams to be opened and the NS upstream of the affected flow streams, based on the existing extrapolation algorithm, estimate the corresponding absolute connectivity value when the change rate of P / H / Fi is equal to the temporary allowable change rate after the next opening.

[0082] It is worth noting that, according to the extrapolation algorithm, if it is estimated that a certain Fi will become 0 before the absolute connectivity becomes 1, then in this step, the absolute connectivity of the variable is specially treated as 1. According to the extrapolation algorithm, if it is estimated that all Fi will become 0 before the absolute connectivity becomes 1, then in this step, the absolute connectivity of all variables in the phase is specially treated as 1. If the following situation exists in a phase of a certain stream of the above stream, the corresponding absolute connectivity needs special treatment: the last successful Fi is less than the lower limit of the component flow, but ∑Fi is greater than the sum of the lower limits of all component flows, then the absolute connectivity corresponding to the Fi less than the lower limit of the component flow is _Fi=1; If ∑Fi of the last successful connection is less than or equal to the sum of the lower limits of all component flows, then absolute connectivity_P=1, absolute connectivity_H=1, and absolute connectivity_Fi=1.

[0083] Take the smallest absolute connectivity among all the above variables and record it as absolute connectivity -MIN. Then determine whether it is less than or equal to 1. If yes, execute step Q; if not, execute step O.

[0084] Step O: Set the relative connectivity of the N streams to be connected to 1. At this time, the absolute connectivity is also 1. Solve the global simultaneous equations EO. Then determine whether the solution is successful. If successful, exit to indicate that the connection is successful (automatic adjustment of connectivity is successful); if unsuccessful, execute step P.

[0085] Step P: Modify the temporary allowable change rate of P / H / Fi of the downstream of the N to-be-connected flows: temporary allowable change rate = temporary allowable change rate / 2. Determine whether the modified temporary allowable change rate is greater than or equal to the minimum allowable change rate; if yes, return and execute step N; if not, exit to indicate that the connection has failed (automatic adjustment of the connection degree has failed).

[0086] Step Q: Convert the absolute connectivity -MIN to the relative connectivity -MIN. Set the relative connectivity of the N streams to be connected to the above relative connectivity -MIN. Solve the global simultaneous equations EO. Then determine whether the solution is successful. If successful, return and execute step K; if unsuccessful, execute step P.

[0087] In the embodiment of the present invention, Figure 3 The schematic diagram of the circulating stream shown in the figure is used as an example to compare the existing opening method and the method of the present invention. The figure shows a simple chemical process flow, which is composed of 4 unit modules and 5 streams. Among them, B2→B3→B4→B2 constitutes a loop, and S2, S3, and S5 are all circulating streams.

[0088] B1 is the material source, and its configuration is: flash type selects pressure-temperature; the pressure is 100kPa; the temperature is 25 degrees Celsius; the flow type selects molar flow; the total flow is 1000kmol / hr; the effective phase is gas-liquid phase; the composition type selects mole fraction; the component proportions include 0.8 CO and 0.2 N2. B2 is a mixer, and its configuration is: pressure / pressure drop selects 0kPa; the pressure drop type selects minimum pressure; the effective phase selects gas-liquid. B3 is a splitter, and its configuration is: the logistics separation ratio of circulating stream S4 and circulating stream S3. B4 is a heater, and its configuration is: flash type selects pressure-heat load; the pressure is 100kPa; the heat load is 0kw; the thermal efficiency is 1; the effective phase selects gas-liquid; the pressure drop parameter is not calculated.

[0089] In this embodiment, the circulating stream S5 is selected to be opened. To facilitate horizontal comparison, the initial values ​​of the downstream variables of S5 are set to: temperature = 150°C, pressure = 100kPa, specific enthalpy = -51615.55kJ / kmol, total flow rate = 1000kmol / h, CO component fraction is 50%, and N2 component fraction is 50%.

[0090] In the first case, when the existing simultaneous equation method is used to open up the system, the upstream and downstream deviation variables required by the present invention are not selected, and the pressure, temperature, total flow rate, and the fraction of each component are used as the upstream and downstream variables of S5, and the pressure deviation, temperature deviation, total flow rate deviation, and the fraction deviation of each component are used as the upstream and downstream deviation variables of S5.

[0091] Set S5 to an empty connection so that the downstream variable is a known variable, and the upstream variable and the upstream and downstream deviation variable are unknown variables.

[0092] Enter the initial value of the downstream variable of S5. Run globally, the calculation is successful, and the result is: The downstream variables of S5 are: pressure = 100 kPa; temperature = 25°C; total flow rate = 1000 kmol / h; CO component fraction is 50%; N2 component fraction is 50%.

[0093] The upstream variables of S5 are: pressure = 100 kPa; temperature = 25°C; total flow rate = 1980 kmol / h; CO component fraction is 65%; N2 component fraction is 35%.

[0094] The upstream and downstream deviation variables of S5 are: pressure deviation = 0 kPa; temperature deviation = 0°C; total flow deviation = -980 kmol / h; CO component fraction deviation = -15%; N2 component fraction deviation = 15%.

[0095] Set S5 to real connection, so that the upstream and downstream deviation variables are known variables, and the upstream and downstream variables are unknown variables. Set the relative connection degree of S5 to 0.05. Then, the next time you run: The upstream and downstream deviation variables of S5 will be changed to: pressure deviation = 0*(1-0.05) = 0kPa; temperature deviation = 0*(1-0.05) = 0℃; total flow deviation = -980*(1-0.05) = -931kmol / h; CO component fraction deviation = -15%*(1-0.05) = -14.25%; N2 component fraction deviation = 15%*(1-0.05) = 14.25%.

[0096] Global operation, calculation failed. The reasons for failure are as follows: According to the material balance, it can be calculated that according to the total flow deviation, CO component fraction deviation, and N2 component fraction deviation calculated previously, the mathematical solutions of the CO / N2 component fractions upstream and downstream of S5 are: CO component fraction downstream of S5 = -18.325%, N2 component fraction = 118.325%. CO component fraction upstream of S5 = -4.075%, N2 component fraction = 104.075%. It can be seen that the mathematical solution of the component fraction is a negative value or a value greater than 100%, which will lead to the failure of the thermodynamic calculation, and from the perspective of chemical engineering, a negative component fraction is unreasonable in itself, so it is equivalent to no solution. In other words, the upstream and downstream deviation variables cannot simultaneously satisfy the total flow deviation = -931kmol / h, CO component fraction deviation = -14.25%, and N2 component fraction deviation = 14.25%. That is, the existing method of opening up is prone to failure.

[0097] In the second case, when the existing simultaneous equation method is used to open up the system, the upstream and downstream deviation variables required by the present invention are not selected, and the pressure, temperature, specific enthalpy, total flow rate, and the fraction of each component are used as the upstream and downstream variables of S5, and the pressure deviation, temperature deviation, specific enthalpy deviation, total flow rate deviation, and the fraction deviation of each component are used as the upstream and downstream deviation variables of S5.

[0098] Set S5 to an empty connection so that the downstream variable is a known variable, and the upstream variable and the upstream and downstream deviation variable are unknown variables.

[0099] Enter the initial value of the downstream variable of S5. Run globally, the calculation is successful, and the result is: The downstream variables of S5 are: pressure = 100 kPa; temperature = 25°C; specific enthalpy = -51615.55 kJ / kmol; total flow rate = 1000 kmol / h; CO component fraction is 50%; N2 component fraction is 50%.

[0100] The upstream variables of S5 are: pressure = 100 kPa; temperature = 87.59°C; specific enthalpy = -70023.82 kJ / kmol; total flow rate = 1980 kmol / h; CO component fraction is 65%; N2 component fraction is 35%.

[0101] The upstream and downstream deviation variables of S5 are: pressure deviation = 0kPa; temperature deviation = 62.41℃; specific enthalpy deviation = 18408.28kJ / kmol; total flow deviation = -980kmol / h. CO component rate deviation = -15%; N2 component rate deviation = 15%; Set S5 to real connection, so that the upstream and downstream deviation variables are known variables, and the upstream and downstream variables are unknown variables. Set the relative connection degree of S5 to 0.01. Then, the next time you run: The upstream and downstream deviation variables of S5 will be changed to: pressure deviation = 0*(1-0.01) = 0kPa; temperature deviation = 62.41*(1-0.01) = 61.78℃; specific enthalpy deviation = 18408.28*(1-0.01) = 18224.19kJ / kmol; total flow deviation = -980*(1-0.01) = -970.2kmol / h; CO component flow deviation = -15%*(1-0.01) = -14.85%; N2 component flow deviation = 15%*(1-0.01) = 14.85%.

[0102] The calculation failed in the global operation. The reasons for the failure are as follows: If the temperature deviation is removed, the calculation is successful, and the results are as follows: The calculation results of the upstream variables of S5 are: pressure = 100kPa; temperature = 147.52℃; specific enthalpy = -52348.2kJ / kmol; total flow rate = 2950.2kmol / h; CO component fraction is 50.597%; N2 component fraction is 49.403%.

[0103] The calculation results of the downstream variables of S5 are: pressure = 100 kPa; temperature = 208.98°C; specific enthalpy = -34124 kJ / kmol; total flow = 1980 kmol / h; CO component fraction is 35.747%; N2 component fraction is 64.253%.

[0104] It can be seen that at this time, the upstream and downstream temperature deviation of S5 = 208.98-147.52 = 61.46℃, and we can inversely calculate the relative connectivity = 1-61.46 / 62.41 = 0.0152≠0.01, that is, when the specific enthalpy deviation decreases by 1%, the temperature deviation must decrease by 1.52% in order to successfully solve the problem. Therefore, if the specific enthalpy deviation and the temperature deviation are reduced by 1% at the same time, there must be no solution.

[0105] In the third case, the upstream and downstream deviation variables required by the present invention are selected for connection and solution, and the pressure, specific enthalpy, total flow rate, and the fraction of each component are used as the upstream and downstream variables of S5, and the pressure deviation, enthalpy flow deviation, total flow deviation, and flow deviation of each component are used as the upstream and downstream deviation variables of S5.

[0106] Set S5 to an empty connection so that the downstream variable is a known variable, and the upstream variable and the upstream and downstream deviation variable are unknown variables.

[0107] Enter the initial value of the downstream variable of S5. Run globally, the calculation is successful, and the result is: The downstream variables of S5 are (i.e. the initial values ​​input): pressure = 100 kPa; specific enthalpy = -51615.55 kJ / kmol; total flow rate = 1000 kmol / h; CO component fraction is 50%; N2 component fraction is 50%.

[0108] The upstream variables of S5 are: pressure = 100 kPa; specific enthalpy = -70023.82 kJ / kmol; total flow rate = 1980 kmol / h; CO component fraction is 65%; N2 component fraction is 35%.

[0109] The upstream and downstream deviation variables of S5 are: pressure deviation = 0kPa; enthalpy flow deviation = 24175.45kW; total flow deviation = -980kmol / h; CO component flow deviation = -787kmol / h; N2 component flow deviation = -193kmol / h; Set S5 to real connection, so that the upstream and downstream deviation variables are known variables, and the upstream and downstream variables are unknown variables. Set the connectivity of S5 to 0.05. Then, the next time you run: The upstream and downstream deviation variables of S5 will be changed to: pressure deviation = 0*(1-0.05) = 0kPa; enthalpy flow deviation = 24175.45*(1-0.05) = 22966.68kW; total flow deviation = -980*(1-0.05) = -931kmol / h; CO component flow deviation = -787*(1-0.05) = -747.65kmol / h; N2 component flow deviation = -193*(1-0.05) = -183.35kmol / h.

[0110] Run globally, the calculation is successful, and the results are as follows: The upstream variables of S5 are: pressure = 100 kPa; specific enthalpy = -83363.35 kJ / kmol; total flow = 6831 kmol / h; CO component fraction is 75.87%; N2 component fraction is 24.13%.

[0111] The downstream variables of S5 are: pressure = 100 kPa; specific enthalpy = -82504.25 kJ / kmol; total flow rate = 5900 kmol / h; CO component fraction is 75.17%; N2 component fraction is 24.83%.

[0112] Repeat the above steps, gradually reduce the connection degree to 0, and finally successfully open the circulation stream S5. The result is: The upstream and downstream variables of S5 are: pressure = 100 kPa; specific enthalpy = -88432.10 kJ / kmol; total flow rate = 99000 kmol / h; CO component fraction is 80%; N2 component fraction is 20%.

[0113] The above embodiments are further elaborations and illustrations of the present invention for ease of understanding, and are not limitations of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for opening up circulating streams in chemical process simulation, characterized in that: include: Determine upstream and downstream deviation variables and upstream and downstream variables; When the absolute connectivity is 0, solve the problem and record the variable value of the successful stream. In the relative adjustment stage, a temporary allowable change rate is preset and the relative connectivity is calculated in combination with the variable values; Solving the problem by dividing the stages according to the relative connectivity; If successful, it enters the absolute adjustment stage and records the variable values ​​of the stream, otherwise it returns to the relative adjustment stage; In the absolute adjustment stage, the temporary allowable change rate is corrected, and the absolute connectivity is calculated based on the variable values ​​after the previous successful connection solution; the connection solution is performed; The absolute adjustment phase is repeated until the absolute connectivity is 1.

2. A method for opening up circulating streams in chemical process simulation according to claim 1, characterized in that: The upstream and downstream deviation variables are at least two of the pressure deviation in the circulating stream and the deviation of the physical item of the extensive property in the circulating stream; The upstream and downstream variables are a combination of variables corresponding to the upstream and downstream deviation variables.

3. A method for opening up circulating streams in chemical process simulation according to claim 1 or 2, characterized in that: In the relative adjustment stage, a temporary allowable change rate is preset, and the relative connectivity is calculated in combination with the variable value; If the relative connectivity is greater than 1, the solution is solved with the absolute connectivity of 1; If the solution is successful, the connection is completed; If the solution is unsuccessful, or the stage-divided breakthrough solution is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition, and the relative connectivity is recalculated; Otherwise, the absolute connectivity is calculated based on the relative connectivity, and the solution is solved by dividing the stages.

4. A method for opening up circulating streams in chemical process simulation according to claim 3, characterized in that: The calculation of the relative connectivity includes: obtaining the variable value of the flow stream after the last successful solution; For any downstream variable, the relative connectivity of the variable is obtained by multiplying the value of the variable by the temporary allowable change rate of the variable and dividing it by the value of the upstream and downstream deviation variable corresponding to the variable. Traverse the relative connectivity of all variables and select the smallest one as the final relative connectivity.

5. A method for opening up circulating streams in chemical process simulation according to claim 1 or 2, characterized in that: In the absolute adjustment stage, the temporary allowable change rate is corrected according to the second preset condition, and the absolute connectivity is calculated in combination with the variable value after the previous successful connection solution; If the absolute connectivity is greater than 1, the solution is solved with the absolute connectivity of 1; If the solution is successful, the connection is completed; If the solution is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition and the absolute connectivity is recalculated.

6. A method for opening up circulating streams in chemical process simulation according to claim 5, characterized in that: In the absolute adjustment stage, if the absolute connectivity is less than or equal to 1, the absolute connectivity is converted into relative connectivity, and a connection solution is performed; If the solution is successful, the variable value of the flow stream after the success is recorded, and after the temporary allowable change rate is corrected according to the second preset condition, the absolute connectivity is recalculated in combination with the latest recorded variable value; If the solution is unsuccessful, the temporary allowable change rate is corrected according to the first preset condition and the absolute connectivity is recalculated.

7. A method for opening up circulating streams in chemical process simulation according to claim 5, characterized in that: The calculation of the absolute connectivity includes: obtaining the variable value of the stream after the last successful solution; For any variable, calculate the absolute connectivity corresponding to the variable’s change rate after the next solution is equal to the temporary allowable change rate of the variable; Traverse all variables and select the smallest one as the final absolute connectivity.

8. The method for opening up circulating streams in chemical process simulation according to claim 3, characterized in that: In the relative adjustment stage, the temporary allowable change rate of any downstream variable is numerically equal to the reference allowable change rate of the variable. When the downstream variable value is less than or equal to the corresponding upstream variable value, it takes a positive sign, otherwise it takes a negative sign.

9. A method for opening up circulating streams in chemical process simulation according to claim 1 or 2 or 4 or 6 or 7 or 8, characterized in that: The first preset condition includes: The previous temporary permissible change rate shall be halved to become the new temporary permissible change rate; Determine whether the new temporary allowed change rate is greater than or equal to the preset minimum allowed change rate. If so, the temporary allowed change rate is corrected; otherwise, the connection fails.

10. The method for opening up circulating streams in chemical process simulation according to claim 5, characterized in that: In the absolute adjustment stage, the second preset condition includes: obtaining the variable value of the stream after the last successful solution; For any variable, the maximum value between the reference allowable change rate of the variable and the actual change rate of the variable after the last successful solution is selected as the temporary allowable change rate of the variable. When the downstream variable value corresponding to the variable is less than or equal to the corresponding upstream variable value, the positive sign is taken, otherwise the negative sign is taken.

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