An optimization control method and device for a special-shaped heat exchange network

Abstract

The application discloses a kind of optimization control method and device of special-shaped heat exchange network, including the outlet of heat exchanger on heat exchange confluence branch is equivalent to k equivalent temperature points;The temperature value of each equivalent temperature point is calculated respectively using the ratio of heat exchanger outlet temperature on each target heat exchange branch to total outlet temperature;Determine branch average temperature value based on the temperature value of each equivalent temperature point and the heat exchanger outlet temperature of other each heat exchange branch except the confluence into heat exchange confluence branch;Determine the branch temperature deviation value of each heat exchange branch based on branch average temperature value;Determine the flow target value of each heat exchange branch based on branch temperature deviation value, and use the flow target value of each heat exchange branch to adjust the flow of n heat exchange branches.The application solves the technical problem that after the confluence of special-shaped heat exchange network branch, the flow of confluence branch after confluence cannot be controlled according to the temperature of branch before confluence.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger network control technology, and in particular to an optimized control method and apparatus for irregularly shaped heat exchangers. Background Technology

[0002] In the oil refining industry, the atmospheric and vacuum distillation unit, as the core unit for primary crude oil processing, accounts for approximately 25%-35% of the total energy consumption of the entire plant. Among them, the energy recovery efficiency of the heat exchange network system directly determines the overall energy efficiency level of the unit.

[0003] Optimizing the heat exchanger network is a key direction for energy-saving retrofitting of atmospheric and vacuum distillation units. This involves increasing the final temperature of the heat exchanger network and reducing the energy consumption of the unit while keeping the process flows within the network constant. Traditional heat exchanger network optimization focuses on improving the thermal efficiency of the heat exchangers and modifying the network structure.

[0004] However, when the heat exchange network structure is fixed, especially when the heat exchange network structure is irregular, it is urgent to solve how to reasonably control the flow rate of each heat exchanger based on the temperature of the process flow after heat exchange, so as to achieve the goal of increasing the final heat exchange temperature. Summary of the Invention

[0005] This invention provides an optimized control method and apparatus for irregularly shaped heat exchange networks, which solves the technical problem that after the branches converge, the flow rate of the branches after convergence cannot be controlled based on the branch temperature before convergence.

[0006] This invention provides an optimized control method for an irregularly shaped heat exchange network. The irregularly shaped heat exchange network includes n heat exchange branches, n≥2; among the n heat exchange branches, there are m heat exchange confluence branches, m≥1, wherein each heat exchange confluence branch is formed by the convergence of at least two heat exchange branches; crude oil passes through the m heat exchange confluence branches and the other heat exchange branches (excluding those confluenced to form the heat exchange confluence branches) and then converges into a flash distillation tower. The control method includes:

[0007] The outlet of the heat exchanger on the heat exchange confluence branch is equivalent to k equivalent temperature points, where k is the number of target heat exchange branches, and the target heat exchange branches are the heat exchange branches that converge to the corresponding heat exchange confluence branch, n≥k≥2.

[0008] The temperature values ​​of each equivalent temperature point are calculated using the ratio of the heat exchanger outlet temperature on each target heat exchange branch to the total outlet temperature, wherein the total outlet temperature is the heat exchanger outlet temperature on the heat exchange confluence branch.

[0009] The average temperature of a branch is determined based on the temperature values ​​of each of the equivalent temperature points and the heat exchanger outlet temperatures of each of the heat exchange branches other than those that converge into the heat exchange confluence branch.

[0010] The branch temperature deviation value of each heat exchange branch is determined based on the average branch temperature value.

[0011] The target flow rate of each heat exchange branch is determined based on the branch temperature deviation value, and the flow rate of each heat exchange branch is adjusted using the target flow rate of each heat exchange branch.

[0012] Further, determining the target flow rate of each heat exchange branch based on the branch temperature deviation value, and adjusting the flow rate of the n heat exchange branches using the target flow rate of each heat exchange branch includes:

[0013] The total temperature deviation of the irregular heat exchange network is determined based on the branch temperature deviation value.

[0014] The flow rate deviation of each heat exchange branch is determined by the branch temperature deviation and the total temperature deviation.

[0015] The target flow value of the flow controller for each heat exchange branch is determined based on the flow deviation value of each heat exchange branch and the current output value of the level controller of the flash tower.

[0016] The flow rate of each of the n heat exchange branches is adjusted based on the target flow rate value of each heat exchange branch.

[0017] Furthermore, the temperature values ​​of each equivalent temperature point are calculated using the ratio of the heat exchanger outlet temperature to the total outlet temperature on each of the target heat exchange branches, including:

[0018] Using formula Calculate the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch, where TI mk TI represents the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. p TI represents the heat exchanger outlet temperature on the heat exchange confluence branch. m0k The heat exchanger outlet temperature is the temperature of the target heat exchange branch on the m-th heat exchange confluence branch.

[0019] Further, determining the branch average temperature value based on the temperature values ​​of each of the equivalent temperature points and the heat exchanger outlet temperatures of each of the other heat exchange branches besides the confluence branch includes:

[0020] Using formula Determine the average temperature value of the branch;

[0021] in, TI represents the average temperature value of the branch. mk TI represents the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. b The heat exchanger outlet temperature is the temperature of the heat exchange branch other than the heat exchange confluence branch, and a is the total number of heat exchange branches used to form the heat exchange confluence branch, n≥a≥k.

[0022] Furthermore, determining the branch temperature deviation value of each heat exchange branch based on the branch average temperature value includes:

[0023] Using formula Determine the branch temperature deviation of the target heat exchange branch, where dT mk The branch temperature deviation value of the target heat exchange branch of the m-th heat exchange confluence branch;

[0024] Using formula Determine the branch temperature deviation value for each of the heat exchange branches other than the branch that merges into the heat exchange confluence branch, where dT b The branch temperature deviation value of the heat exchange branch in clause b, excluding the heat exchange confluence branch.

[0025] Furthermore, determining the total temperature deviation of the irregular heat exchange network based on the branch temperature deviation values ​​includes:

[0026] Using formula Determine the total temperature deviation of the irregular heat exchange network, where T i >0, T s The total temperature deviation, dT i Let be the branch temperature deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

[0027] Furthermore, determining the flow rate deviation value of each heat exchange branch using the branch temperature deviation and the total temperature deviation includes:

[0028] Using formula Determine the flow deviation value for each branch;

[0029] in, f is the flow deviation value of the heat exchange branch described in the i-th clause. ud To set the flow rate regulation speed parameter, dT i Let n be the branch temperature deviation value of the i-th heat exchange branch, i = mk, or i = na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n ≥ a ≥ k, and T. s This represents the total temperature deviation.

[0030] Furthermore, determining the target flow rate value of the flow controller for each heat exchange branch based on the flow rate deviation value of each heat exchange branch and the current output value of the level controller of the flash tower includes:

[0031] Using formula Determine the target flow value for the flow controller of each branch;

[0032] in, Let be the target flow rate of the flow controller for the i-th heat exchange branch, and LIC01.MV be the current output value of the level controller for the flash tower. Let be the flow deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

[0033] This invention also provides an optimized control device for an irregularly shaped heat exchange network, wherein the irregularly shaped heat exchange network includes n heat exchange branches, n≥2; among the n heat exchange branches, there are m heat exchange merging branches, m≥1, wherein each heat exchange merging branch is formed by the convergence of at least two heat exchange branches; crude oil, after passing through the heat exchange of the m heat exchange merging branches and the other heat exchange branches excluding those merging into the heat exchange merging branches, converges and enters a flash distillation tower, and the control device includes:

[0034] An equivalent modeling unit is used to represent the outlet of the heat exchanger on the heat exchange confluence branch as k equivalent temperature points, where k is the number of target heat exchange branches, and the target heat exchange branches are the heat exchange branches that converge to the corresponding heat exchange confluence branch, n≥k≥2.

[0035] An equivalent temperature calculation unit is used to calculate the temperature value of each of the equivalent temperature points by using the ratio of the heat exchanger outlet temperature on each of the target heat exchange branches to the total outlet temperature, wherein the total outlet temperature is the heat exchanger outlet temperature on the heat exchange confluence branch.

[0036] The average temperature calculation unit is used to determine the average temperature value of the branch based on the temperature value of each of the equivalent temperature points and the heat exchanger outlet temperature of each of the heat exchange branches other than the heat exchange confluence branch.

[0037] Temperature deviation calculation unit is used to determine the branch temperature deviation value of each heat exchange branch based on the branch average temperature value.

[0038] The target flow rate determination unit is used to determine the target flow rate value of each heat exchange branch based on the branch temperature deviation value, and to adjust the flow rate of the n heat exchange branches using the target flow rate value of each heat exchange branch.

[0039] This invention also provides an irregularly shaped heat exchange network, which includes an optimization control device for the irregularly shaped heat exchange network, and further includes n heat exchange branches, a flash tower, a liquid level controller, n flow controllers, and n flow regulating valves; wherein,

[0040] The level controller is connected to the flash tower; all n flow controllers are connected to the level controller.

[0041] One end of each of the n heat exchange branches is connected to a flow controller via a flow regulating valve.

[0042] The other end of k heat exchange branches merges into a heat exchange confluence branch, where n≥k≥2;

[0043] The number of heat exchange confluence branches is m, where m ≥ 1;

[0044] The other ends of each of the heat exchange confluence branches and other heat exchange branches, except those that merge into the heat exchange confluence branches, are connected to the flash tower after merging.

[0045] Heat exchangers are installed on both the heat exchange branch and the heat exchange confluence branch.

[0046] This invention discloses an optimization control method and apparatus for an irregularly shaped heat exchanger network. The control method includes: equating the outlet of the heat exchanger on the heat exchange confluence branch to k equivalent temperature points; calculating the temperature value of each equivalent temperature point using the ratio of the heat exchanger outlet temperature on each target heat exchange branch to the total outlet temperature; determining the branch average temperature value based on the temperature values ​​of each equivalent temperature point and the heat exchanger outlet temperatures of all heat exchange branches except the confluence branch; determining the branch temperature deviation value of each heat exchange branch based on the branch average temperature value; determining the flow target value of each heat exchange branch based on the branch temperature deviation value; and adjusting the flow rate of n heat exchange branches using the flow target value of each heat exchange branch. This invention establishes equivalent temperature points to transform irregularly shaped heat exchange networks into regular heat exchange networks. By using the temperature values ​​of the equivalent temperature points to determine the corresponding temperature deviations, the target flow values ​​of each branch are determined. This solves the technical problem that after the branches converge, the flow rate of the branches after convergence cannot be controlled based on the branch temperatures before convergence. This invention achieves the technical effect of improving the final temperature and heat exchange efficiency of irregularly shaped heat exchange networks. Attached Figure Description

[0047] Figure 1 This is a structural diagram of an irregular heat exchange network provided in an embodiment of the present invention;

[0048] Figure 2 This is a flowchart of an optimized control method for an irregularly shaped heat exchange network provided in an embodiment of the present invention;

[0049] Figure 3 This is a flowchart of another optimized control method for irregular heat exchange networks provided in an embodiment of the present invention;

[0050] Figure 4 This is a flowchart illustrating the implementation process of the optimized control method for irregular heat exchange networks provided in this embodiment of the invention.

[0051] Figure 5 This is a structural diagram of an optimized control device for a non-circular heat exchange network provided in an embodiment of the present invention. Detailed Implementation

[0052] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0053] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this invention are used to distinguish different objects, not to limit a specific order. The various embodiments of this invention described below can be performed individually or in combination with each other; the embodiments of this invention do not impose specific limitations in this regard.

[0054] This invention provides an optimized control method for an irregularly shaped heat exchange network. The network comprises n heat exchange branches (n≥2), and m merging branches (m≥1) among these branches. Each merging branch is formed by the convergence of at least two heat exchange branches. Crude oil passes through the m merging branches and the other heat exchange branches (excluding those forming the merging branches) before converging and entering a flash tower. For example, taking an irregularly shaped heat exchange network with n=4 heat exchange branches, and m=1 merging branches among these branches, formed by the convergence of a first and a second heat exchange branch, this invention provides an example to illustrate the optimized control method for an irregularly shaped heat exchange network.

[0055] Figure 1 This is a structural diagram of an irregular heat exchange network provided in an embodiment of the present invention. Figure 2 This is a flowchart of an optimized control method for an irregularly shaped heat exchanger network provided in an embodiment of the present invention.

[0056] For example, such as Figure 1 As shown, the irregular heat exchange network includes four heat exchange branches. The first heat exchange branch 11 and the second heat exchange branch 12 merge into a combined heat exchange branch 20. After heat exchange through the combined heat exchange branch 20, the third heat exchange branch 13, and the fourth heat exchange branch 14, the crude oil converges and enters the flash tower 10. (See also...) Figure 1 Among them, the heat exchanger on the first heat exchange branch 11 is E02, the heat exchanger on the second heat exchange branch 12 is E03, the heat exchanger on the heat exchange confluence branch 20 is E01, the heat exchanger on the third heat exchange branch 13 is E04, and the heat exchanger on the fourth heat exchange branch 14 is E05.

[0057] like Figure 2 As shown, the optimization control method for this irregular heat exchanger network specifically includes the following steps:

[0058] S101, the outlet of the heat exchanger on the heat exchange confluence branch is equivalent to k equivalent temperature points, where k is the number of target heat exchange branches, and the target heat exchange branches are the heat exchange branches that merge into the corresponding heat exchange confluence branch, n≥k≥2.

[0059] For example, when k=2, such as Figure 1 As shown, the outlet of heat exchanger E01 on the heat exchange confluence branch 20 is equivalent to two equivalent temperature points, namely the first equivalent temperature point T12 and the second equivalent temperature point T13, where the equivalent temperatures at the first equivalent temperature point T12 and the second equivalent temperature point T13 are respectively TI 11 and TI 12 .

[0060] S102, calculate the temperature value of each equivalent temperature point by using the ratio of the heat exchanger outlet temperature on each target heat exchange branch to the total outlet temperature, where the total outlet temperature is the heat exchanger outlet temperature on the heat exchange confluence branch.

[0061] For example, such as Figure 1 As shown, the heat exchanger outlet temperature TI on the first heat exchange branch 11 is used. 101 and the heat exchanger outlet temperature TI on the second heat exchange branch 12 102 Total export temperature TI 01 The ratios are used to calculate the temperature values ​​at the first equivalent temperature point T12 and the second equivalent temperature point T13, respectively. The total outlet temperature is the heat exchanger outlet temperature TI on the heat exchange confluence branch 20. 01 .

[0062] Optionally, S102 specifically includes: using the formula Calculate the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch, where TI mk Let TI be the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. p TI is the heat exchanger outlet temperature on the heat exchange confluence branch. m0k Let be the heat exchanger outlet temperature on the k-th target heat exchange branch of the m-th heat exchange confluence branch.

[0063] For example, see Figure 1Using the formula Calculate the temperature value of the first equivalent temperature point T12 in the first heat exchange confluence branch, where TI 11 The temperature value of the first equivalent temperature point T12, TI 01 The heat exchanger outlet temperature on heat exchange confluence branch 20, TI 101 The heat exchanger outlet temperature on the first heat exchange branch 11, TI 102 The outlet temperature of the heat exchanger on the second heat exchange branch 12.

[0064] Using formula Calculate the temperature value of the second equivalent temperature point T13 in the first heat exchange confluence branch, where TI 12 This is the temperature value at the second equivalent temperature point T13.

[0065] S103, the average temperature value of the branch is determined based on the temperature value of each equivalent temperature point and the heat exchanger outlet temperature of each heat exchange branch other than the branch that merges into a heat exchange confluence.

[0066] For example, see Figure 1 Based on the temperature value TI at the first equivalent temperature point T12 11 The temperature value TI at the second equivalent temperature point T13 12 The average temperature of the branch is determined by the heat exchanger outlet temperature TI1 of the third heat exchange branch 13 and the heat exchanger outlet temperature TI2 of the fourth heat exchange branch 14. .

[0067] Optionally, S103 specifically includes: using the formula Determine the average temperature value of the branch circuit;

[0068] in, The average temperature of the branch is TI. mk Let TI be the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. b n represents the heat exchanger outlet temperature of the heat exchange branches other than those that merge into a heat exchange confluence branch, and a represents the total number of heat exchange branches used to merge into a heat exchange confluence branch, where n ≥ a ≥ k.

[0069] For example, see Figure 1 Using the formula Determine the average temperature value of the branch; among which, The average temperature of the branch is TI. 11 TI represents the temperature value of the first equivalent temperature point T12 in the first heat exchange confluence branch. 12 TI1 is the temperature value of the second equivalent temperature point T13 of the first heat exchange confluence branch, TI1 is the heat exchanger outlet temperature of the third heat exchange branch 13, and TI2 is the heat exchanger outlet temperature of the fourth heat exchange branch 14.

[0070] S104, determine the branch temperature deviation value of each heat exchange branch based on the average branch temperature value.

[0071] Optionally, S104 specifically includes: determining the branch temperature deviation value of each heat exchange branch based on the branch average temperature value, including:

[0072] Using formula Determine the branch temperature deviation of the target heat exchange branch, where dT mk The branch temperature deviation value of the k-th target heat exchange branch in the m-th heat exchange confluence branch;

[0073] Using formula Determine the branch temperature deviation values ​​for each heat exchange branch other than the branch that merges into a heat exchange confluence, where dT b This refers to the branch temperature deviation value of the b-th heat exchange branch among all heat exchange branches except for the confluence branch that forms the heat exchange merge branch.

[0074] For example, see Figure 1 Using the formula Determine the branch temperature deviation value of the first target heat exchange branch (i.e., the first heat exchange branch 11) of the first heat exchange confluence branch, where dT 11 This is the branch temperature deviation value of the first heat exchange branch 11;

[0075] Using formula Determine the branch temperature deviation value of the second target heat exchange branch (i.e., the second heat exchange branch 12) of the first heat exchange confluence branch, where dT 12 This is the branch temperature deviation value of the second heat exchange branch 12;

[0076] Using formula Determine the branch temperature deviation value of the first heat exchange branch (i.e. the third heat exchange branch 13) among all heat exchange branches except the branch that merges into a heat exchange confluence branch, where dT1 is the branch temperature deviation value of the third heat exchange branch 13.

[0077] Using formula Determine the branch temperature deviation value of the second heat exchange branch (i.e., the fourth heat exchange branch 14) among all heat exchange branches except the confluence branch, where dT2 is the branch temperature deviation value of the fourth heat exchange branch 14.

[0078] S105, determine the target flow rate of each heat exchange branch based on the branch temperature deviation value, and use the target flow rate of each heat exchange branch to adjust the flow rate of n heat exchange branches.

[0079] Specifically, after determining the branch temperature deviation of each heat exchange branch, the total temperature deviation of the irregular heat exchange network is calculated based on the branch temperature deviation of each heat exchange branch. Then, the flow regulation speed parameter for each flow adjustment cycle is defined, and the flow deviation value of each branch is determined based on the flow regulation speed parameter, the branch temperature deviation of each branch, and the total temperature deviation. Finally, the flow target value of the flow controller of each branch is determined based on the flow deviation value of each branch and the current output value of the liquid level controller of the flash tower.

[0080] After determining the target flow value of the flow controller for each branch, the flow controller of each branch is controlled by the target flow value to adjust the flow and achieve the purpose of increasing the final temperature of the heat exchange network.

[0081] This invention establishes equivalent temperature points to transform irregularly shaped heat exchange networks into regular heat exchange networks. By using the temperature values ​​of the equivalent temperature points to determine the corresponding temperature deviations, the target flow values ​​of each branch are determined. This solves the technical problem that after the branches converge, the flow rate of the branches after convergence cannot be controlled based on the branch temperatures before convergence. This invention achieves the technical effect of improving the final temperature and heat exchange efficiency of irregularly shaped heat exchange networks.

[0082] Based on the above technical solutions, Figure 3 This is a flowchart of another optimized control method for irregularly shaped heat exchange networks provided in an embodiment of the present invention, such as... Figure 3 As shown, S105 specifically includes:

[0083] S301, determine the total temperature deviation of the irregular heat exchange network based on the branch temperature deviation value.

[0084] Optionally, S301 specifically includes: using the formula Determine the total temperature deviation of the irregular heat exchanger network, where T i >0, T s For the total temperature deviation, dT i Let be the branch temperature deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

[0085] For example, see Figure 1 Using the formula Determine the total temperature deviation of the irregular heat exchanger network, specifically... .

[0086] S302, the flow rate deviation of each heat exchange branch is determined by the branch temperature deviation and the total temperature deviation.

[0087] Optionally, S302 specifically includes: using the formula Determine the flow deviation value for each branch;

[0088] in, Let f be the flow deviation value of the i-th heat exchange branch. ud To set the flow rate regulation speed parameter, dT i Let n be the branch temperature deviation value of the i-th heat exchange branch, i = mk, or i = na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n ≥ a ≥ k, and T. s This represents the total temperature deviation.

[0089] S303, determine the target flow value of the flow controller for each heat exchange branch based on the flow deviation value of each heat exchange branch and the current output value of the level controller of the flash tower.

[0090] Optionally, S303 specifically includes: using the formula Determine the target flow value for the flow controller of each branch;

[0091] in, Let LIC01.MV be the target flow rate of the flow controller for the i-th heat exchange branch, and let LIC01.MV be the current output value of the level controller for the flash tower. Let be the flow deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

[0092] S304, Flow regulation is performed on n heat exchange branches based on the target flow value of each heat exchange branch.

[0093] Specifically, after determining the target flow value of the flow controller for each heat exchange branch, the flow controller of each heat exchange branch is controlled by the target flow value to adjust the flow and achieve the purpose of increasing the final temperature of the heat exchange network.

[0094] The following specific embodiment illustrates the optimized control method for irregular heat exchange networks provided in this invention.

[0095] Figure 4 This is a flowchart illustrating the implementation process of the optimized control method for irregular heat exchange networks provided in this embodiment of the invention.

[0096] See Figure 4 After the system is powered on, it first performs initialization and parameter setting; then it determines whether it is within the adjustment cycle. If not, it performs a judgment on whether the termination condition is met. If yes, the system sequentially performs reading temperature measurement values, calculating the equivalent temperature of the branch, calculating the target flow value of each branch, setting the target flow value of each branch, and then enters the step of judging whether the termination condition is met. If the judgment result is met, it ends directly. If the judgment result is not met, it returns to the step of judging whether it is within the adjustment cycle.

[0097] For example, taking the heat exchange network before the crude oil desalting in a petrochemical atmospheric and vacuum distillation unit as an example, its structure is as follows: Figure 1 As shown, crude oil enters the heat exchange network through four heat exchange branches, each with a different heat exchanger deployment. After passing through heat exchangers E02 and E03, the crude oil merges into a heat exchange confluence branch 20, and then passes through heat exchanger E01. The flow controllers for the four heat exchange branches are FIC01, FIC02, FIC03, and FIC04, respectively. The temperature measurement points for the four heat exchange branches are shown in the figure: TI 01 =145.32℃, TI 101 =119.88℃, TI 102 =122.09℃, TI1=137.22℃, TI2=115.46℃; where TI 01 It is the outlet temperature of heat exchanger E01, TI 101 It is the outlet temperature of heat exchanger E02, TI 102 TI1 is the outlet temperature of heat exchanger E03, TI2 is the outlet temperature of heat exchanger E04, and TI3 ​​is the outlet temperature of heat exchanger E05.

[0098] The level controller LIC01 of the flash tower 10 is a basic PID (Proportional-Integral-Derivative) controller. Based on the level measurement value (i.e., the current output value mentioned above) and the set value, the target flow rate of the four heat exchange branches is calculated. The output of the level controller LIC01 is 330 t / h. TC01 is the core temperature equalization controller.

[0099] First, based on the five temperature measurement points, the theoretical temperatures of the four heat exchange branches are estimated, that is, the temperature values ​​of the first equivalent temperature point T12 and the second equivalent temperature point T13 are calculated:

[0100] ;

[0101] ;

[0102] Second, calculate the average temperature of the branch:

[0103] ;

[0104] Third, calculate the branch temperature deviation value for each branch:

[0105] ;

[0106] ;

[0107] ;

[0108] ;

[0109] Fourth, calculate the total temperature deviation of the irregular heat exchanger network:

[0110] Since the deviation value of the fourth heat exchange branch is negative, it is not included in the total temperature deviation.

[0111] Fifth, set the flow rate adjustment speed parameter, with a maximum adjustment speed of f for each adjustment cycle. ud =0.03;

[0112] Sixth, calculate the flow deviation of each branch within the adjustment period:

[0113] ;

[0114] ;

[0115] ;

[0116] ;

[0117] Seventh, calculate the flow setpoint for each branch. The output of the level controller LIC01 is 330. Including the calculation deviation of the core temperature controller, the setpoints of the flow controller are as follows:

[0118] FIC 11 SP = 330.012 t / h;

[0119] FIC 12 SP = 330.016 t / h;

[0120] FIC1.SP = 330.002 t / h;

[0121] FIC2.SP=329.97 t / h;

[0122] This process continues iteratively until the equivalent temperature difference of the four branches reaches the specified range.

[0123] In summary, the initial equivalent temperature difference of the four heat exchange branches was 31.18℃. After three hours of optimized control based on the irregular heat exchange network, the equivalent temperature difference of the four heat exchange branches became 20.02℃. The final heat exchange temperature increased from 132.1℃ to 135.8℃. The application of this invention improved the thermal efficiency of the irregular heat exchange network, which is of great benefit to a 10 million ton / year atmospheric and vacuum distillation unit.

[0124] Figure 5 This is a structural diagram of an optimized control device for an irregular heat exchange network provided in an embodiment of the present invention.

[0125] The irregular heat exchange network includes n heat exchange branches, n≥2; among the n heat exchange branches, there are m heat exchange confluence branches, m≥1, where each heat exchange confluence branch is formed by the convergence of at least two heat exchange branches; the crude oil, after heat exchange through the m heat exchange confluence branches and other heat exchange branches excluding those confluence branches, converges and enters the flash tower. The control device includes:

[0126] Equivalent modeling unit 51 is used to equate the outlet of the heat exchanger on the heat exchange confluence branch to k equivalent temperature points, where k is the number of target heat exchange branches, and the target heat exchange branches are the heat exchange branches that merge into the corresponding heat exchange confluence branch, n≥k≥2.

[0127] The equivalent temperature calculation unit 52 is used to calculate the temperature value of each equivalent temperature point by using the ratio of the heat exchanger outlet temperature on each target heat exchange branch to the total outlet temperature, wherein the total outlet temperature is the heat exchanger outlet temperature on the heat exchange confluence branch.

[0128] The average temperature calculation unit 53 is used to determine the average temperature value of the branch based on the temperature value of each equivalent temperature point and the heat exchanger outlet temperature of each heat exchange branch except for the heat exchange confluence branch.

[0129] Temperature deviation calculation unit 54 is used to determine the branch temperature deviation value of each heat exchange branch based on the branch average temperature value.

[0130] The target flow determination unit 55 is used to determine the target flow value of each heat exchange branch based on the branch temperature deviation value, and to adjust the flow of n heat exchange branches using the target flow value of each heat exchange branch.

[0131] Optionally, the target flow determination unit 55 includes:

[0132] The first calculation subunit is used to determine the total temperature deviation of the irregular heat exchanger network based on the branch temperature deviation value.

[0133] The second calculation subunit is used to determine the flow deviation value of each heat exchange branch by using the branch temperature deviation and the total temperature deviation of each heat exchange branch.

[0134] The third determining subunit is used to determine the flow target value of the flow controller of each heat exchange branch based on the flow deviation value of each heat exchange branch and the current output value of the liquid level controller of the flash tower.

[0135] The flow regulation subunit is used to regulate the flow of n heat exchange branches based on the target flow value of each heat exchange branch.

[0136] Optionally, the equivalent temperature calculation unit 52 is specifically used for:

[0137] Using formula Calculate the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch, where TI mk Let TI be the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. p TI is the heat exchanger outlet temperature on the heat exchange confluence branch. m0k Let be the heat exchanger outlet temperature on the k-th target heat exchange branch of the m-th heat exchange confluence branch.

[0138] Optionally, the average temperature calculation unit 53 is specifically used for:

[0139] Using formula Determine the average temperature value of the branch circuit;

[0140] in, The average temperature of the branch is TI. mk Let TI be the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. b n represents the heat exchanger outlet temperature of the heat exchange branches other than those that merge into a heat exchange confluence branch, and a represents the total number of heat exchange branches used to merge into a heat exchange confluence branch, where n ≥ a ≥ k.

[0141] Optionally, the temperature deviation calculation unit 54 is specifically used for:

[0142] Using formula Determine the branch temperature deviation of the target heat exchange branch, where dT mk The branch temperature deviation value of the k-th target heat exchange branch in the m-th heat exchange confluence branch;

[0143] Using formula Determine the branch temperature deviation values ​​for each heat exchange branch other than the branch that merges into a heat exchange confluence, where dT b This refers to the branch temperature deviation value of the b-th heat exchange branch among all heat exchange branches except for the confluence branch that forms the heat exchange merge branch.

[0144] Optionally, the first computational subunit is specifically used for:

[0145] Using formula Determine the total temperature deviation of the irregular heat exchanger network, where T i >0, T s For the total temperature deviation, dT i Let be the branch temperature deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

[0146] Optionally, the second computational subunit is specifically used for:

[0147] Using formula Determine the flow deviation value for each branch;

[0148] in, f is the flow deviation value of the i-th heat exchange branch. ud To set the flow rate regulation speed parameter, dT i Let n be the branch temperature deviation value of the i-th heat exchange branch, i = mk, or i = na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n ≥ a ≥ k, and T. s This represents the total temperature deviation.

[0149] Optionally, the third computational subunit is specifically used for:

[0150] Using formula Determine the target flow value for the flow controller of each branch;

[0151] in, Let LIC01.MV be the target flow rate of the flow controller for the i-th heat exchange branch, and let LIC01.MV be the current output value of the level controller for the flash tower. Let be the flow deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

[0152] The optimization control device for irregular heat exchange networks provided in this embodiment of the invention has the same technical features as the optimization control method for irregular heat exchange networks provided in the above embodiments, so it can also solve the same technical problems and achieve the same technical effects.

[0153] This invention also provides an irregular heat exchange network, which includes the optimized control device for the irregular heat exchange network in any of the above embodiments, and further includes n heat exchange branches, a flash tower, a liquid level controller, n flow controllers, and n flow regulating valves; wherein, the liquid level controller is connected to the flash tower; all n flow controllers are connected to the liquid level controller; one end of each of the n heat exchange branches is connected to a flow controller through a flow regulating valve; the other ends of the k heat exchange branches merge to form a heat exchange confluence branch, n≥k≥2; the number of heat exchange confluence branches is m, m≥1; the other ends of each heat exchange confluence branch and other heat exchange branches excluding those merging to form a heat exchange confluence branch are connected to the flash tower after merging; heat exchangers are provided on the heat exchange branches and the heat exchange confluence branches.

[0154] For example, such as Figure 1As shown, the irregular heat exchange network also includes four heat exchange branches (first heat exchange branch 11, second heat exchange branch 12, third heat exchange branch 13, and fourth heat exchange branch 14), a flash tower 10, a level controller LIC01, four flow controllers (FIC01, FIC02, FIC03, and FIC04), and four flow regulating valves (FV1, FV2, FV3, and FV4); wherein, the level controller LIC01 is connected to the flash tower 10; and all four flow controllers are connected to the level controller LIC01.

[0155] One end of each of the four heat exchange branches is connected to a flow controller via a flow regulating valve;

[0156] The other ends of the two heat exchange branches (i.e., the first heat exchange branch 11 and the second heat exchange branch 12) converge to form the heat exchange confluence branch 20; the number of heat exchange confluence branches is 1.

[0157] The other ends of the heat exchange confluence branch 20, the third heat exchange branch 13, and the fourth heat exchange branch 14 converge and are connected to the flash tower 10; heat exchangers (E01, E02, E03, E04, E05) are installed on the heat exchange branches and the heat exchange confluence branch.

[0158] The irregular heat exchange network provided in this embodiment includes the optimized control device for the irregular heat exchange network in the above embodiments. Therefore, the irregular heat exchange network provided in this embodiment also has the beneficial effects described in the above embodiments, which will not be repeated here.

[0159] In the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0160] Finally, it should be noted that the above are merely preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. An optimized control method for an irregularly shaped heat exchanger network, characterized in that, The irregular heat exchange network includes n heat exchange branches, n≥2; among the n heat exchange branches, there are m heat exchange confluence branches, m≥1, wherein each heat exchange confluence branch is formed by the convergence of at least two heat exchange branches; the crude oil, after passing through the heat exchange of the m heat exchange confluence branches and the other heat exchange branches excluding those confluenced into the heat exchange confluence branches, converges and enters the flash distillation tower, and the control method includes: The outlet of the heat exchanger on the heat exchange confluence branch is equivalent to k equivalent temperature points, where k is the number of target heat exchange branches, and the target heat exchange branches are the heat exchange branches that converge to the corresponding heat exchange confluence branch, n≥k≥2. The temperature values ​​of each equivalent temperature point are calculated using the ratio of the heat exchanger outlet temperature on each target heat exchange branch to the total outlet temperature, wherein the total outlet temperature is the heat exchanger outlet temperature on the heat exchange confluence branch. The average temperature of a branch is determined based on the temperature values ​​of each of the equivalent temperature points and the heat exchanger outlet temperatures of each of the heat exchange branches other than those that converge into the heat exchange confluence branch. The branch temperature deviation value of each heat exchange branch is determined based on the average branch temperature value. The target flow rate of each heat exchange branch is determined based on the branch temperature deviation value, and the flow rate of each heat exchange branch is adjusted using the target flow rate of each heat exchange branch. The calculation of the temperature value of each equivalent temperature point using the ratio of the heat exchanger outlet temperature to the total outlet temperature on each of the target heat exchange branches includes: Using formula Calculate the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch, where TI mk TI represents the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. p TI represents the heat exchanger outlet temperature on the heat exchange confluence branch. m0k The heat exchanger outlet temperature is the temperature of the target heat exchange branch on the m-th heat exchange confluence branch.

2. The optimized control method for irregularly shaped heat exchange networks according to claim 1, characterized in that, Determining the target flow rate for each heat exchange branch based on the branch temperature deviation value, and then adjusting the flow rate of the n heat exchange branches using the target flow rate for each heat exchange branch, includes: The total temperature deviation of the irregular heat exchange network is determined based on the branch temperature deviation value. The flow rate deviation of each heat exchange branch is determined by the branch temperature deviation and the total temperature deviation. The target flow value of the flow controller for each heat exchange branch is determined based on the flow deviation value of each heat exchange branch and the current output value of the level controller of the flash tower. The flow rate of each of the n heat exchange branches is adjusted based on the target flow rate value of each heat exchange branch.

3. The optimized control method for irregularly shaped heat exchange networks according to claim 2, characterized in that, The average branch temperature value is determined based on the temperature values ​​of each of the equivalent temperature points and the heat exchanger outlet temperatures of all heat exchange branches except those that converge into the heat exchange confluence branch. Using formula Determine the average temperature value of the branch; in, TI represents the average temperature value of the branch. mk TI represents the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. b The heat exchanger outlet temperature is the temperature of the heat exchange branch other than the heat exchange confluence branch, and a is the total number of heat exchange branches used to form the heat exchange confluence branch, n≥a≥k.

4. The optimized control method for the irregular heat exchange network according to claim 3, characterized in that, The branch temperature deviation values ​​for each heat exchange branch are determined based on the average branch temperature values, including: Using formula Determine the branch temperature deviation of the target heat exchange branch, where dT mk The branch temperature deviation value of the target heat exchange branch of the m-th heat exchange confluence branch; Using formula Determine the branch temperature deviation value for each of the heat exchange branches other than the branch that merges into the heat exchange confluence branch, where dT b The branch temperature deviation value of the heat exchange branch in clause b, excluding the heat exchange confluence branch.

5. The optimized control method for irregular heat exchange networks according to claim 2, characterized in that, The total temperature deviation of the irregular heat exchange network is determined based on the branch temperature deviation values, including: Using formula Determine the total temperature deviation of the irregular heat exchange network, where T i >0, T s dT is the total temperature deviation. i Let be the branch temperature deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

6. The optimized control method for irregular heat exchange networks according to claim 2, characterized in that, Determining the flow rate deviation value of each heat exchange branch using the branch temperature deviation and the total temperature deviation includes: Using formula Determine the flow deviation value for each branch; in, f is the flow deviation value of the heat exchange branch described in the i-th clause. ud To set the flow rate regulation speed parameter, dT i Let n be the branch temperature deviation value of the i-th heat exchange branch, i = mk, or i = na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n ≥ a ≥ k, and T. s This represents the total temperature deviation.

7. The optimized control method for irregular heat exchange networks according to claim 2, characterized in that, The target flow value of the flow controller for each heat exchange branch is determined based on the flow deviation value of each heat exchange branch and the current output value of the level controller of the flash tower, including: Using formula Determine the target flow value for the flow controller of each branch; Where FICi.SP is the target flow rate of the flow controller for the i-th heat exchange branch, and LIC01.MV is the current output value of the level controller for the flash tower. Let be the flow deviation value of the i-th heat exchange branch, i=mk, or i=na, where a is the total number of heat exchange branches used to merge into a heat exchange confluence branch, n≥a≥k.

8. An optimized control device for an irregularly shaped heat exchange network, characterized in that, The irregular heat exchange network includes n heat exchange branches, n≥2; among the n heat exchange branches, there are m heat exchange confluence branches, m≥1, wherein each heat exchange confluence branch is formed by the convergence of at least two heat exchange branches; the crude oil, after passing through the heat exchange of the m heat exchange confluence branches and the other heat exchange branches excluding those confluenced into the heat exchange confluence branches, converges and enters the flash distillation tower. The control device includes: An equivalent modeling unit is used to represent the outlet of the heat exchanger on the heat exchange confluence branch as k equivalent temperature points, where k is the number of target heat exchange branches, and the target heat exchange branches are the heat exchange branches that converge to the corresponding heat exchange confluence branch, n≥k≥2. An equivalent temperature calculation unit is used to calculate the temperature value of each of the equivalent temperature points by using the ratio of the heat exchanger outlet temperature on each of the target heat exchange branches to the total outlet temperature, wherein the total outlet temperature is the heat exchanger outlet temperature on the heat exchange confluence branch. The average temperature calculation unit is used to determine the average temperature value of the branch based on the temperature value of each of the equivalent temperature points and the heat exchanger outlet temperature of each of the heat exchange branches other than the heat exchange confluence branch. Temperature deviation calculation unit is used to determine the branch temperature deviation value of each heat exchange branch based on the branch average temperature value. The target flow rate determination unit is used to determine the target flow rate value of each heat exchange branch based on the branch temperature deviation value, and to adjust the flow rate of the n heat exchange branches using the target flow rate value of each heat exchange branch. The equivalent temperature calculation unit is specifically used for: Using formula Calculate the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch, where TI mk TI represents the temperature value of the k-th equivalent temperature point in the m-th heat exchange confluence branch. p TI represents the heat exchanger outlet temperature on the heat exchange confluence branch. m0k The heat exchanger outlet temperature is the temperature of the target heat exchange branch on the m-th heat exchange confluence branch.

9. An irregularly shaped heat exchange network, characterized in that, The irregular heat exchange network includes the optimized control device for the irregular heat exchange network as described in claim 8, and further includes n heat exchange branches, a flash tower, a liquid level controller, n flow controllers, and n flow regulating valves; wherein, The level controller is connected to the flash tower; all n flow controllers are connected to the level controller. One end of each of the n heat exchange branches is connected to a flow controller via a flow regulating valve. The other end of k heat exchange branches merges into a heat exchange confluence branch, where n≥k≥2; The number of heat exchange confluence branches is m, where m ≥ 1; The other ends of each of the heat exchange confluence branches and other heat exchange branches, except those that merge into the heat exchange confluence branches, are connected to the flash tower after merging. Heat exchangers are installed on both the heat exchange branch and the heat exchange confluence branch.

Images