A method, system, apparatus, and readable medium for controlling load and ethylene concentration

Abstract

This invention provides a method, system, device, and readable medium for controlling load and ethylene concentration using a combination of multivariate coordination and soft sensing. The method includes the following steps: obtaining a total ethylene load control model for a first loop reactor and a second loop reactor; dynamically adjusting the ethylene feed flow rate into the two reactors based on the setpoints and measured values ​​of the ethylene concentration in the two reactors to balance the ethylene concentration; establishing a soft sensing model of ethylene concentration characteristic values ​​and related variables; calculating the characteristic value of the current ethylene concentration and the target value of the characteristic value based on the soft sensing model; and adjusting the catalyst feed flow rate based on the current characteristic value of the ethylene concentration and the target value of the characteristic value. This method considers both the influence of the catalyst feed rate on the ethylene concentration and the influence of the distribution of ethylene between the two reactors on the ethylene concentration, thus ensuring the stability of the total reactor load.

Description

Technical Field

[0001] This invention relates to the field of double-loop liquid-phase polyethylene production technology, and in particular to a method, system, equipment, and readable medium for controlling load and ethylene concentration by combining multivariate coordination and soft measurement. Background Technology

[0002] The dual-loop liquid-phase polyethylene process uses two loop reactors to produce polyethylene. Ethylene is dissolved in isobutane solvent and enters both loop reactors. The effluent from the first loop reactor enters the second loop reactor, and the chromium catalyst is added only in the first loop reactor. In the dual-loop liquid-phase polyethylene unit, the ethylene concentration in the reactors affects the polymerization yield and production safety. With a constant total ethylene load, the ethylene feed flow rates into both reactors remain constant. Operators manually adjust the catalyst feed flow rate into the first reactor to control the ethylene concentration in both reactors within a certain range.

[0003] The existing adjustment methods have two drawbacks:

[0004] (1) The hysteresis of ethylene concentration is large and heavily dependent on the operator's experience. Manual adjustment may result in untimely adjustment or over-adjustment, causing large fluctuations in ethylene concentration in the two reactors.

[0005] (2) For a dual-loop reactor system, there is only one adjustment method, namely the catalyst flow rate entering the first reactor, but there are two controlled variables, namely the ethylene concentration in the first reactor and the second reactor. This means that in some cases, only the control target of the ethylene concentration in one reactor can be prioritized. Summary of the Invention

[0006] To address the above technical problems, this invention provides a method, system, device, and readable medium for controlling load and ethylene concentration by combining multivariate coordination and soft measurement. This invention considers both the influence of catalyst feed rate on ethylene concentration and the influence of ethylene distribution between the two reactors on ethylene concentration through the control scheme, while also ensuring the stability of the total reactor load.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A method for controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement, for a dual-loop liquid-phase polyethylene plant, the dual-loop liquid-phase polyethylene plant comprising a first loop reactor and a second loop reactor, includes the following steps:

[0009] Step 1: Ethylene Distribution Control: The total ethylene load control model of the first loop reactor and the second loop reactor is obtained through the host computer. After the total ethylene load stabilizes, the ethylene feed flow rate entering the first loop reactor and the second loop reactor is dynamically adjusted according to the set value and measured value of the ethylene concentration in the first loop reactor and the second loop reactor to balance the ethylene concentration in the first loop reactor and the second loop reactor.

[0010] Step 2: Establish a soft measurement model of ethylene concentration characteristic values ​​and related variables using soft measurement instruments, and calculate the current ethylene concentration characteristic value and the target value of the characteristic value based on the soft measurement model;

[0011] Step 3: Based on the current characteristic value of ethylene concentration and the target value of the characteristic value, adjust the catalyst feed flow rate to control the ethylene concentration in the first loop reactor and the second loop reactor.

[0012] In a preferred embodiment of the present invention, during the ethylene distribution control process, the total ethylene load control model includes a mode in which the total ethylene load remains constant, a mode in which the total ethylene load decreases, or a mode in which the total ethylene load increases. In each mode, the ethylene feed flow rate entering the first loop reactor and the second loop reactor is dynamically adjusted based on the set and measured values ​​of the ethylene concentration in the first loop reactor and the second loop reactor.

[0013] In a preferred embodiment of the present invention, under the mode of keeping the total ethylene load constant, the method for distributing the ethylene feed flow rate is as follows:

[0014] If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor.

[0015] If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor.

[0016] If α1>β1 and α2<β2, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor; otherwise, increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor.

[0017] Wherein, α1 is the measured value of ethylene concentration in the first loop reactor, α2 is the measured value of ethylene concentration in the second loop reactor, β1 is the set value of ethylene concentration in the first loop reactor, and β2 is the set value of ethylene concentration in the second loop reactor.

[0018] In a preferred embodiment of the present invention, under the mode of increased total ethylene load, the ethylene feed flow rate of the first loop reactor and the ethylene feed flow rate of the second loop reactor are increased respectively. The method for allocating the increase in the ethylene feed flow rate of the two reactors is as follows:

[0019] If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor.

[0020] If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor.

[0021] If α1>β1 and α2<β2, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor; otherwise, the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor.

[0022] Wherein, α1 is the measured value of ethylene concentration in the first loop reactor, α2 is the measured value of ethylene concentration in the second loop reactor, β1 is the set value of ethylene concentration in the first loop reactor, and β2 is the set value of ethylene concentration in the second loop reactor.

[0023] In a preferred embodiment of the present invention, under the mode of reduced total ethylene load, the ethylene feed flow rate of the first loop reactor and the ethylene feed flow rate of the second loop reactor are reduced respectively. The method for allocating the reduction in the ethylene feed flow rate of the two reactors is as follows:

[0024] If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor.

[0025] If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor.

[0026] If α1>β1 and α2<β2, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor; otherwise, the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor.

[0027] Wherein, α1 is the measured value of ethylene concentration in the first loop reactor, α2 is the measured value of ethylene concentration in the second loop reactor, β1 is the set value of ethylene concentration in the first loop reactor, and β2 is the set value of ethylene concentration in the second loop reactor.

[0028] In a preferred embodiment of the present invention, the calculation formula for the soft sensor model in step two is specifically as follows:

[0029]

[0030] Where λ is the characteristic value of ethylene concentration, ε1, ε2, ε3, ε4 are coefficients, τ1, τ2 are the average residence times of isobutane in the first loop reactor and the second loop reactor, respectively, m1, m2 are the mass flow rates of isobutane in the first loop reactor and the second loop reactor, respectively, and V1, V2 are the volumes of the first and second reactors.

[0031] If C1 and C2 are the current ethylene concentration measurements in the first loop reactor and the second loop reactor, respectively, then λ is the characteristic value of the current ethylene concentration.

[0032] If C1 and C2 are the setpoints for ethylene concentration in the first loop reactor and the second loop reactor, respectively, then λ is the target value for the current ethylene concentration characteristic value.

[0033] In a preferred embodiment of the present invention, step three specifically involves: if the current ethylene concentration characteristic value is less than the target value of the characteristic value, then the catalyst feed flow rate is reduced; otherwise, the catalyst feed flow rate is increased.

[0034] Based on the same inventive concept, the present invention also provides a system for controlling load and ethylene concentration by combining multivariate coordination and soft measurement, comprising:

[0035] The data acquisition module is used to collect the ethylene concentration measurement values ​​in the first loop reactor and the second loop reactor.

[0036] The ethylene feed flow rate adjustment execution module receives data from the data acquisition module, receives and acquires the ethylene total load control model of the first loop reactor and the second loop reactor, and dynamically adjusts the ethylene feed flow rate entering the first loop reactor and the second loop reactor according to the ethylene concentration set value and measured value in the first loop reactor and the second loop reactor to balance the ethylene concentration in the first loop reactor and the second loop reactor.

[0037] The soft measurement calculation module establishes a soft measurement model of the current ethylene concentration characteristic value and related variables, and calculates the current ethylene concentration characteristic value and the target value of the characteristic value based on the soft measurement model;

[0038] The catalyst flow rate adjustment module adjusts the catalyst feed flow rate based on the current ethylene concentration characteristic value and the target value of the characteristic value, thereby controlling the ethylene concentration in the first loop reactor and the second loop reactor.

[0039] Based on the same inventive concept, the present invention also provides an apparatus for controlling load and ethylene concentration by combining multivariate coordination and soft measurement, including a memory and a processor. The memory stores computer-readable instructions, and when the processor executes the computer-readable instructions, it implements the above-described method for controlling load and ethylene concentration by combining multivariate coordination and soft measurement.

[0040] Based on the same inventive concept, the present invention also provides a computer-readable medium storing a computer program that, when executed by one or more processors, implements the above-described method for controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement.

[0041] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art:

[0042] The method for controlling load and ethylene concentration by combining multivariate coordination and soft sensing provided by this invention not only considers traditional adjustment methods, namely catalyst feed flow rate, but also adjusts the distribution of ethylene feed in the two reactors in real time, making the ethylene concentration in the two reactors more uniform. When adjusting the catalyst feed flow rate, the ethylene concentration in one reactor is no longer used as the target, but rather a soft sensing model is established by integrating the ethylene concentration in both reactors and other relevant variables. The current characteristic value of the ethylene concentration in the reactor is used as the controlled variable, thereby achieving more stable control of the ethylene concentration in both reactors. Moreover, the method of this invention greatly reduces the labor intensity of on-site operators, avoids misoperation, and effectively ensures the safe operation of the equipment. Attached Figure Description

[0043] Figure 1 This is a simplified flowchart of the double-ring polyethylene reaction process;

[0044] Figure 2 This is a logic diagram for the distribution of ethylene feed flow rate under the condition of constant total ethylene load. In the diagram, ε1 and ε2 are the adjustment amounts of ethylene in the first loop reactor and the second loop reactor. If ε1>0, it means that the ethylene feed flow rate of the first loop reactor is increased; if ε1<0, it means that the ethylene feed flow rate of the first loop reactor is decreased. If ε2>0, it means that the ethylene feed flow rate of the second loop reactor is increased; if ε2<0, it means that the ethylene feed flow rate of the second loop reactor is decreased.

[0045] Figure 3 This is the logic diagram for the distribution of ethylene feed flow rate under the condition of constant total ethylene load. If the total ethylene load increases, then ε1 and ε2 are both greater than 0; if the total ethylene load decreases, then ε1 and ε2 are both less than 0.

[0046] Figure 4 This is the control logic for the catalyst feed flow rate;

[0047] Figure 5 The ethylene concentration trend in the first loop reactor is shown, where (a) represents manual operation in the background art and (b) represents the method of the present invention.

[0048] Figure 6 The ethylene concentration trend in the second loop reactor is shown, where (a) represents manual operation in the background art and (b) represents the method of the present invention.

[0049] Explanation of reference numerals in the attached drawings: 1-First loop reactor; 2-Second loop reactor; 3-Axial flow pump; 4-Ethylene concentration detector for the first loop reactor; 5-Ethylene concentration detector for the second loop reactor; 6-Catalyst feed flow regulating valve; 7-Isobutane feed flow regulating valve; 9-Ethylene feed flow regulating valve. Detailed Implementation

[0050] It should be noted that:

[0051] Application scenarios of the present invention are as follows Figure 1 As shown, the dual-loop liquid-phase polyethylene unit includes a first loop reactor 1 and a second loop reactor 2. Ethylene, the raw material, is dissolved in isobutane solvent and enters both the first loop reactor 1 and the second loop reactor 2. A catalyst is added to the first loop reactor 1. Therefore, both the first loop reactor 1 and the second loop reactor 2 are equipped with isobutane feed flow regulating valves 7 and ethylene feed flow regulating valves 9. The first loop reactor 1 is also equipped with a catalyst feed flow regulating valve 6. The product from the outlet of the first loop reactor 1 enters the second loop reactor 2. The outlet of the second loop reactor 2 yields a mixed slurry of polyethylene and isobutane, which is sent to subsequent processing stages. Since the two loop reactors contain a solid-liquid two-phase system, an axial flow pump 3 provides power for material circulation. During production, the ethylene concentration in the first loop reactor 1 and the second loop reactor 2 is measured using an ethylene concentration detector 4 in the first loop reactor and an ethylene concentration detector 5 in the second loop reactor.

[0052] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method, system, apparatus, and readable medium for controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement. The advantages and features of the invention will become clearer from the following description.

[0053] Example 1

[0054] A method for controlling load and ethylene concentration by combining multivariate coordination and soft sensing includes the following steps:

[0055] Step 1: Ethylene Distribution Control: The total ethylene load control model of the first loop reactor and the second loop reactor is obtained through the host computer. After the total ethylene load stabilizes, the ethylene feed flow rate entering the first loop reactor and the second loop reactor is dynamically adjusted according to the set value and measured value of the ethylene concentration in the first loop reactor and the second loop reactor to balance the ethylene concentration in the first loop reactor and the second loop reactor.

[0056] Step 2: Establish a soft measurement model of ethylene concentration characteristic values ​​and related variables using soft measurement instruments, and calculate the current ethylene concentration characteristic value and the target value of the characteristic value based on the soft measurement model;

[0057] Step 3: Based on the current characteristic value of ethylene concentration and the target value of the characteristic value, adjust the catalyst feed flow rate to control the ethylene concentration in the first loop reactor and the second loop reactor.

[0058] 1. In the ethylene distribution control process of step one, the ethylene total load control model includes a constant ethylene total load mode, a decreasing ethylene total load mode, or an increasing ethylene total load mode. In each mode, the ethylene feed flow rate into the first and second loop reactors is dynamically adjusted based on the set and measured values ​​of the ethylene concentration in the first and second loop reactors. If the measured ethylene concentration in one loop reactor is lower than the set value, the ethylene feed flow rate in that loop reactor will be increased. Correspondingly, to maintain a stable total ethylene output, the ethylene feed flow rate in the other loop reactor will be reduced. When production conditions change and an increase in ethylene load is required, the ethylene feed flow rate in both the first and second loop reactors will be increased simultaneously. If the ethylene concentration in one loop reactor is significantly higher than the set value, the increased ethylene feed flow rate in that loop reactor will be less than that in the other reactor, thus balancing the ethylene concentration in the first and second loop reactors.

[0059] The controller model structure is shown in Table 1. The more "★" marks in the table, the higher the priority. The higher the priority, the more priority is given to ensuring the control objective of that variable. "+" and "-" in the table indicate the direction of action. "+" indicates that the input variable has a positive effect on the output variable, and "-" indicates a negative effect.

[0060] Table 1. Controller Model Structure for Ethylene Distribution

[0061]

[0062] Specifically: See below Figure 2 Under the condition that the total ethylene load remains constant, the method for distributing the ethylene feed flow rate is as follows:

[0063] If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor.

[0064] If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor.

[0065] If α1>β1 and α2<β2, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor; otherwise, increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor.

[0066] See Figure 3 Under the mode of increased total ethylene load, the ethylene feed flow rate of the first loop reactor and the ethylene feed flow rate of the second loop reactor are increased respectively. The distribution method of the increase in ethylene feed flow rate of the two reactors is as follows:

[0067] If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor.

[0068] If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor.

[0069] If α1>β1 and α2<β2, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor; otherwise, the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor.

[0070] Continue reading Figure 3 Under the mode of reduced total ethylene load, the ethylene feed flow rate of the first loop reactor and the ethylene feed flow rate of the second loop reactor are reduced respectively. The method for allocating the reduction in ethylene feed flow rate of the two reactors is as follows:

[0071] If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor.

[0072] If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor.

[0073] If α1>β1 and α2<β2, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor; otherwise, the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor.

[0074] Wherein, α1 is the measured value of ethylene concentration in the first loop reactor, α2 is the measured value of ethylene concentration in the second loop reactor, β1 is the set value of ethylene concentration in the first loop reactor, and β2 is the set value of ethylene concentration in the second loop reactor.

[0075] 2. In step two, a soft sensor model is established to correlate the ethylene concentration characteristic value with relevant variables in the first and second loop reactors. The specific calculation formula for the soft sensor model is as follows:

[0076]

[0077] Where λ is the characteristic value of ethylene concentration, ε1, ε2, ε3, ε4 are coefficients, τ1, τ2 are the average residence times of isobutane in the first loop reactor and the second loop reactor, respectively, m1, m2 are the mass flow rates of isobutane in the first loop reactor and the second loop reactor, respectively, and V1, V2 are the volumes of the first and second reactors.

[0078] If C1 and C2 are the current ethylene concentration measurements in the first loop reactor and the second loop reactor, respectively, then λ is the characteristic value of the current ethylene concentration.

[0079] If C1 and C2 are the setpoints for ethylene concentration in the first loop reactor and the second loop reactor, respectively, then λ is the target value for the current ethylene concentration characteristic value.

[0080] The current ethylene concentration measurement value is calculated based on the soft measurement model, and then the target value of the current ethylene concentration characteristic value is calculated based on the ethylene concentration set value.

[0081] 3. For details on step three, please refer to [link / reference]. Figure 4 After calculating the characteristic value of the current ethylene concentration and the target value of the characteristic value, the catalyst feed flow rate is adjusted. If the current ethylene concentration characteristic value is less than the target value of the characteristic value, the catalyst feed flow rate is reduced; otherwise, the catalyst feed flow rate is increased.

[0082] To demonstrate the advanced nature and reliability of the method in this embodiment, Figure 5 and Figure 6 The real-time trend of ethylene concentration over 72 hours is shown using the method of this embodiment and using manual operation of catalyst feed flow rate. Using the method of this invention, the standard deviation of ethylene concentration in the first loop reactor is reduced by 49%, and the standard deviation of ethylene concentration in the first loop reactor is reduced by 63%.

[0083] This embodiment, based on process analysis of a dual-loop liquid-phase polyethylene reactor system, designs a method combining multivariate coordination and soft-sensor control of load and ethylene concentration. It proposes a control strategy for real-time allocation of ethylene feed flow rates between the two reactors while maintaining a stable total ethylene load. It also presents a soft-sensor modeling and control method for ethylene concentration characteristic values, solving the problem of insufficient system freedom caused by more controlled variables than manipulated variables. This method considers the impact of catalyst feed rate on ethylene concentration, as well as the impact of ethylene distribution between the two reactors, while also ensuring the stability of the total reactor load. Furthermore, this method significantly reduces the workload of on-site operators, avoids misoperation, and effectively ensures the safe operation of the unit. Simultaneously, the data required for this method is uploaded to a host computer, and all auxiliary calculations, programming, and control algorithms are implemented on the host computer. Finally, the control output is written back to the DCS, reducing the DCS's operating load and improving its safety.

[0084] Example 2

[0085] Based on the same inventive concept, the present invention also provides a system for controlling load and ethylene concentration by combining multivariate coordination and soft measurement, comprising:

[0086] The data acquisition module is used to collect the ethylene concentration measurement values ​​in the first loop reactor and the second loop reactor.

[0087] The ethylene feed flow rate adjustment execution module receives data from the data acquisition module, receives and acquires the ethylene total load control model of the first loop reactor and the second loop reactor, and dynamically adjusts the ethylene feed flow rate into the first loop reactor and the second loop reactor according to the set value and measured value of the ethylene concentration in the first loop reactor and the second loop reactor to balance the ethylene concentration in the first loop reactor and the second loop reactor.

[0088] The soft measurement calculation module establishes a soft measurement model of the current ethylene concentration characteristic value and related variables, and calculates the current ethylene concentration characteristic value and the target value of the characteristic value based on the soft measurement model;

[0089] The catalyst flow rate adjustment module adjusts the catalyst feed flow rate based on the current ethylene concentration characteristic value and the target value of the characteristic value, thereby controlling the ethylene concentration in the first loop reactor and the second loop reactor.

[0090] Example 3

[0091] A device for controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement includes a memory and a processor. The memory stores computer-readable instructions, and when the processor executes the computer-readable instructions, it implements the method of controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement as described in Embodiment 1.

[0092] Example 4

[0093] A computer-readable medium storing a computer program that, when executed by one or more processors, implements the method of multivariate coordination and soft measurement combined with control of load and ethylene concentration as described in Embodiment 1.

[0094] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A method for controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement, for use in a dual-loop liquid-phase polyethylene plant, the dual-loop liquid-phase polyethylene plant comprising a first loop reactor and a second loop reactor, characterized in that, Includes the following steps: Step 1: Ethylene Distribution Control: The total ethylene load control model of the first loop reactor and the second loop reactor is obtained through the host computer. After the total ethylene load stabilizes, the ethylene feed flow rate entering the first loop reactor and the second loop reactor is dynamically adjusted according to the set value and measured value of the ethylene concentration in the first loop reactor and the second loop reactor to balance the ethylene concentration in the first loop reactor and the second loop reactor. Step 2: Establish a soft measurement model of ethylene concentration characteristic values ​​and related variables using soft measurement instruments, and calculate the current ethylene concentration characteristic value and the target value of the characteristic value based on the soft measurement model; Step 3: Based on the current characteristic value of ethylene concentration and the target value of the characteristic value, adjust the catalyst feed flow rate to control the ethylene concentration in the first loop reactor and the second loop reactor.

2. The method for controlling load and ethylene concentration by combining multivariate coordination and soft sensing according to claim 1, characterized in that, During the ethylene distribution control process, the total ethylene load control model includes a mode in which the total ethylene load remains constant, a mode in which the total ethylene load decreases, or a mode in which the total ethylene load increases. In each mode, the ethylene feed flow rate entering the first loop reactor and the second loop reactor is dynamically adjusted based on the set and measured values ​​of the ethylene concentration in the first loop reactor and the second loop reactor.

3. The method for controlling load and ethylene concentration by combining multivariate coordination and soft sensing according to claim 2, characterized in that, Under the mode of keeping the total ethylene load constant, the ethylene feed flow rate is distributed as follows: If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor. If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then decrease the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor. If α1>β1 and α2<β2, then reduce the ethylene feed flow rate of the first loop reactor and increase the ethylene feed flow rate of the second loop reactor. Otherwise, increase the ethylene feed flow rate of the first loop reactor and decrease the ethylene feed flow rate of the second loop reactor; Wherein, α1 is the measured value of ethylene concentration in the first loop reactor, α2 is the measured value of ethylene concentration in the second loop reactor, β1 is the set value of ethylene concentration in the first loop reactor, and β2 is the set value of ethylene concentration in the second loop reactor.

4. The method for controlling load and ethylene concentration by combining multivariate coordination and soft sensing according to claim 2, characterized in that, Under the mode of increased total ethylene load, the ethylene feed flow rate of the first loop reactor and the ethylene feed flow rate of the second loop reactor are increased respectively. The method for allocating the increase in the ethylene feed flow rate of the two reactors is as follows: If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor. If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor. If α1>β1 and α2<β2, then the increase in ethylene feed flow rate of the first loop reactor is less than the increase in ethylene feed flow rate of the second loop reactor; otherwise, the increase in ethylene feed flow rate of the first loop reactor is greater than the increase in ethylene feed flow rate of the second loop reactor. Wherein, α1 is the measured value of ethylene concentration in the first loop reactor, α2 is the measured value of ethylene concentration in the second loop reactor, β1 is the set value of ethylene concentration in the first loop reactor, and β2 is the set value of ethylene concentration in the second loop reactor.

5. The method for controlling load and ethylene concentration by combining multivariate coordination and soft measurement according to claim 2, characterized in that, Under the mode of reduced total ethylene load, the ethylene feed flow rate of the first loop reactor and the ethylene feed flow rate of the second loop reactor are reduced respectively. The method for allocating the reduction in the ethylene feed flow rate of the two reactors is as follows: If α1 < β1 and α2 < β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1| < |α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor; if |α1-β1| > |α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor. If α1>β1 and α2>β2, then determine the magnitudes of |α1-β1| and |α2-β2|: if |α1-β1|<|α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is less than the decrease in ethylene feed flow rate of the second loop reactor; if |α1-β1|>|α2-β2|, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor. If α1>β1 and α2<β2, then the decrease in ethylene feed flow rate of the first loop reactor is greater than the decrease in ethylene feed flow rate of the second loop reactor. Otherwise, the reduction in ethylene feed flow rate in the first loop reactor will be less than the reduction in ethylene feed flow rate in the second loop reactor. Wherein, α1 is the measured value of ethylene concentration in the first loop reactor, α2 is the measured value of ethylene concentration in the second loop reactor, β1 is the set value of ethylene concentration in the first loop reactor, and β2 is the set value of ethylene concentration in the second loop reactor.

6. The method for controlling load and ethylene concentration by combining multivariate coordination and soft sensing according to claim 1, characterized in that, The specific calculation formula for the soft sensor model in step two is as follows: Where λ is the characteristic value of ethylene concentration, ε1, ε2, ε3, ε4 are coefficients, τ1, τ2 are the average residence times of isobutane in the first loop reactor and the second loop reactor, respectively, m1, m2 are the mass flow rates of isobutane in the first loop reactor and the second loop reactor, respectively, and V1, V2 are the volumes of the first and second reactors. If C1 and C2 are the current ethylene concentration measurements in the first loop reactor and the second loop reactor, respectively, then λ is the characteristic value of the current ethylene concentration. If C1 and C2 are the setpoints for ethylene concentration in the first loop reactor and the second loop reactor, respectively, then λ is the target value for the current ethylene concentration characteristic value.

7. The method for controlling load and ethylene concentration by combining multivariate coordination and soft sensing according to claim 1, characterized in that, Step 3 specifically involves: if the current ethylene concentration characteristic value is less than the target value, then reduce the catalyst feed flow rate; otherwise, increase the catalyst feed flow rate.

8. A system for controlling load and ethylene concentration by combining multivariate coordination and soft measurement, characterized in that, include: The data acquisition module is used to collect the ethylene concentration measurement values ​​in the first loop reactor and the second loop reactor. The ethylene feed flow rate adjustment execution module receives data from the data acquisition module, receives and acquires the ethylene total load control model of the first loop reactor and the second loop reactor, and dynamically adjusts the ethylene feed flow rate entering the first loop reactor and the second loop reactor according to the ethylene concentration set value and measured value in the first loop reactor and the second loop reactor to balance the ethylene concentration in the first loop reactor and the second loop reactor. The soft measurement calculation module establishes a soft measurement model of the current ethylene concentration characteristic value and related variables, and calculates the current ethylene concentration characteristic value and the target value of the characteristic value based on the soft measurement model; The catalyst flow rate adjustment module adjusts the catalyst feed flow rate based on the current ethylene concentration characteristic value and the target value of the characteristic value, thereby controlling the ethylene concentration in the first loop reactor and the second loop reactor.

9. A device for controlling load and ethylene concentration by combining multivariate coordination and soft measurement, characterized in that, The system includes a memory and a processor, the memory storing computer-readable instructions, and the processor, when executing the computer-readable instructions, implementing the method for controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement as described in any one of claims 1-7.

10. A computer-readable medium storing a computer program, characterized in that, When the computer program is executed by one or more processors, it implements the method for controlling load and ethylene concentration using a combination of multivariate coordination and soft measurement as described in any one of claims 1-7.

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