A reactor simulation method and system for catalytic reforming

Abstract

The embodiment of the present application provides a kind of catalytic reforming reactor simulation method and system, the reactor simulation method includes: based on the molar flow of each component of first node and basic step, the molar flow of each component of second node is determined;If the molar flow of each component of the second node exists less than 0 molar flow, then according to the preset proportion reduction the basic step, until the molar flow of each component of the second node is all greater than 0;The step after reduction is recovered to the basic step, based on the molar flow of each component of the second node and the basic step, the molar flow of each component of third node is determined;Cyclic operation, if the molar flow of each component of the third node exists less than 0 molar flow, then according to the preset proportion reduction the basic step, until the molar flow calculation of each component of each node of plug flow reactor is completed.

Description

Technical Field

[0001] The embodiments of this application belong to the field of reactor dynamics modeling technology, and particularly relate to a reactor simulation method and system for catalytic reforming. Background Technology

[0002] Catalytic reforming is a process that transforms naphtha into reformed gasoline rich in aromatics (benzene, toluene, xylene) and produces hydrogen as a byproduct under certain temperature, pressure, hydrogen, and hydrogen conditions.

[0003] In catalytic reforming, calculations are typically performed in segments, with significant differences in reaction rates among components, and some components approaching zero rates during the process. This is due to the strong selectivity of catalytic reforming; favorable reactions such as alkane dehydrogenation, cyclization, and aromatization have high reaction rates, while unfavorable reactions such as hydrocracking have low rates. Existing catalytic reforming models typically use plug flow reactor (PFR) models for solving these problems. However, the integration step size in this model must be pre-determined by manually writing it into the user interface or backend of the program, making it impossible to calculate cases where components approach zero rates. Existing solution algorithms must use very small integration step sizes when encountering cases where some components approach zero rates, and these cannot be adjusted, resulting in inflexible calculations, slow speed, and difficulty in convergence.

[0004] Based on this, a new reactor simulation method and system for catalytic reforming has been developed. Summary of the Invention

[0005] This specification provides a reactor simulation method and system for catalytic reforming to solve some or all of the following problems: Existing catalytic reforming typically uses a plug flow reactor (PFR) model for solution, but the integration step size in this model needs to be manually hardcoded in the operating interface or backend of the program and thus cannot calculate cases where the composition is close to zero. Existing solution algorithms must use a very small integration step size when encountering certain composition near-zero values, and this cannot be adjusted, making the calculation inflexible, slow, and difficult to converge.

[0006] To solve the above-mentioned technical problems, the embodiments in this specification are implemented as follows:

[0007] This specification provides an embodiment of a reactor simulation method for catalytic reforming, the reactor simulation method comprising:

[0008] Based on the molar flow rate of each component at the first node and the basic step size, determine the molar flow rate of each component at the second node.

[0009] If there is a molar flow rate less than 0 in any of the components of the second node, the basic step size is reduced by a preset ratio until the molar flow rate of each component of the second node is greater than 0.

[0010] The reduced step size is restored to the basic step size, and the molar flow rate of each component in the third node is determined based on the molar flow rate of each component in the second node and the basic step size.

[0011] The process is repeated. If any component at the third node has a molar flow rate less than 0, the base step size is reduced according to the preset ratio until the molar flow rate of each component at each node of the plug flow reactor is calculated.

[0012] This specification also provides an embodiment of a reactor simulation system for catalytic reforming, the reactor simulation system comprising:

[0013] The first calculation module determines the molar flow rate of each component in the second node based on the molar flow rate and basic step size of each component in the first node.

[0014] The variable step size calculation module reduces the basic step size by a preset ratio if there is a molar flow rate less than 0 in the molar flow rate of each component in the second node, until the molar flow rate of each component in the second node is greater than 0.

[0015] The second calculation module restores the reduced step size to the basic step size, and determines the molar flow rate of each component in the third node based on the molar flow rate of each component in the second node and the basic step size.

[0016] The loop module operates in a loop. If the molar flow rate of each component at the third node is less than 0, the basic step size is reduced according to the preset ratio until the molar flow rate of each component at each node of the plug flow reactor is calculated.

[0017] The at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects: Based on the molar flow rate of each component of the first node and the basic step size, the molar flow rate of each component of the second node is determined; if there is a molar flow rate less than 0 in the molar flow rate of each component of the second node, the basic step size is reduced according to a preset ratio until the molar flow rate of each component of the second node is greater than 0; the reduced step size is restored to the basic step size, and based on the molar flow rate of each component of the second node and the basic step size, the molar flow rate of each component of the third node is determined; the operation is repeated, and if there is a molar flow rate less than 0 in the molar flow rate of each component of the third node, the basic step size is reduced according to the preset ratio until the molar flow rate calculation of each component of each node of the plug flow reactor is completed. This can reduce the amount of calculation for catalytic reforming reaction, and the calculation speed is fast, the robustness is good, and the accuracy of the calculation results is high. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. Some specific embodiments of this application will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings designate the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0019] Figure 1 A schematic flow diagram of a reactor simulation method for catalytic reforming provided in the embodiments of this specification;

[0020] Figure 2 This is a schematic diagram illustrating the calculation of determining a variable step size, provided as an embodiment of this specification.

[0021] Figure 3 A framework diagram of a reactor simulation method for catalytic reforming provided for embodiments of this specification;

[0022] Figure 4 This is a schematic diagram of a reactor simulation system for catalytic reforming provided in this illustrative embodiment. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort should fall within the scope of protection of the present application.

[0024] The catalytic reforming reaction network involves more than 30 reactants and more than 80 chemical reactions. These reactions can be classified into six major categories based on their reaction type: six-membered cycloalkane dehydrogenation aromatization (DHTA), alkane dehydrogenation cyclization (DHTC), isomerization (ISO, including alkane, cycloalkane isomerization, and aromatic isomerization), aromatic alkyl transfer (TRANS), hydrocracking (HYCR, including alkane cracking and cycloalkane cracking), and aromatic hydroalkylation (HYDE). Table 1 shows the reaction equations for the six major categories of catalytic reforming reactions.

[0025] Table 1

[0026] Reaction name Reaction equation DHTA01 <![CDATA[CH<-->BENZENE+3H2]]> DHTA02 <![CDATA[MCH<-->TOLUENE+3H2]]> DHTC01 <![CDATA[N-HEXANE<-->CH+H2]]> DHTC02 <![CDATA[HEPTANE<-->MCH+H2]]> ISO01 N-HEXANE<-->2MP ISO02 HEPTANE<-->2MHX TRANS01 MXYLENE<-->PXYLENE TRANS02 MXYLENE<-->OXYLENE HYCR01 <![CDATA[ETHANE+H2->2CH4]]> HYCR02 <![CDATA[PROP+H2->ETHANE+CH4]]> HYDE01 <![CDATA[TOLUENE+H2->BENZENE+CH4]]> HYDE02 <![CDATA[PXYLENE+H2->TOLUENE+CH4]]>

[0027] in,

[0028] CH stands for methane;

[0029] BENZENE is benzene;

[0030] H2 is hydrogen gas;

[0031] MCH stands for methylcyclohexane;

[0032] TOLUENE is toluene;

[0033] N-HEXANE is n-hexane;

[0034] HEPTANE is n-heptane;

[0035] MP stands for melamine phosphate.

[0036] MHX is hydrofluoric acid;

[0037] MXYLENE is xylene;

[0038] OXYLENE is o-xylene;

[0039] ETHANE is hexane;

[0040] CH4 represents methane;

[0041] PROP stands for propylene;

[0042] PXYLENE is p-xylene.

[0043] Reforming is a gas-solid phase reaction, with the reactants in the gas phase and the catalyst in the solid phase. Catalytic reforming reactors are typically large in size and have weak mixing, resulting in non-uniform component concentrations throughout the reactor. In simulation calculations, a segmented approach, often referred to as the PFR model, is commonly used. Within each segment, the component concentrations, temperatures, and reaction rates are considered identical. However, these parameters typically differ between segments. The volume of each reactor segment can be understood as a volume step. The component concentration in the current segment can be calculated from the component concentration, reaction rate, and step size of the previous segment. For a complete reactor calculation, the sum of all volume steps equals the reactor volume. For reactors of the same size, more segments increase the computational load, slowing down the calculation and consuming more computational resources. Furthermore, beyond a certain point, the accuracy of the solution does not significantly improve.

[0044] For conventional PFR models, the step size is equal for each segment and is determined before calculation. Reforming reactions have complex reaction networks, involving over thirty substances and 85 reactions. Furthermore, the reaction rates of these 85 reactions vary significantly. Some reactions have high rates, leading to situations where the concentration of one or more components within the reactor approaches zero. In such cases, if the calculated reaction rate in the previous segment is high and the concentration of the participating component is close to zero, a large, fixed step size can easily result in negative calculated component concentrations, leading to errors in the calculation. Conversely, a smaller step size might allow the reforming calculation to succeed, but it will consume more computational resources and take longer.

[0045] Existing fixed-step-size solving algorithms typically cannot calculate the case where some reaction components are close to 0 during the process. This is inherent to the fixed-step-size solving algorithm itself, because when the component is close to 0, the fixed-step-size algorithm can easily calculate the component composition to a negative value, or the calculation step size for the entire reactor can be very small, resulting in a very long calculation time.

[0046] Based on this, this specification proposes a reactor simulation method and system for catalytic reforming. The backtracking algorithm is used to optimize the PFR model solution algorithm for catalytic reforming, so that the step size during the calculation process can be automatically adjusted according to the component content in the calculation process of the PFR model solution algorithm for catalytic reforming. When the calculated component content is close to zero, the step size is reduced; otherwise, the calculation is performed according to the original step size, thereby reducing the amount of calculation and speeding up the calculation. Moreover, it has good robustness.

[0047] Figure 1 This is a schematic flowchart illustrating a reactor simulation method for catalytic reforming provided in an embodiment of this specification. From a programming perspective, the reactor simulation method for catalytic reforming is executed by a program hosted on an application server or application terminal. It is understood that this method can be executed by any device, equipment, platform, or cluster of devices with computing and processing capabilities. Figure 1 As shown, the reactor simulation method includes:

[0048] Step S101: Based on the molar flow rate of each component at the first node and the basic step size, determine the molar flow rate of each component at the second node.

[0049] In the embodiments described in this specification, the basic step length is determined based on the length of the plug flow reactor and the preset number of nodes.

[0050] In specific embodiments, the preset number of nodes can be determined based on empirical values ​​or selected by the user according to system settings. In one embodiment of this specification, the preset number of nodes is 40.

[0051] The basic step length is calculated as the ratio of the length of the plug flow reactor to the preset number of nodes, i.e., basic step length = length of plug flow reactor / preset number of nodes.

[0052] In the embodiments of this specification, determining the molar flow rate of each component at the second node based on the molar flow rate and basic step size of each component at the first node specifically includes:

[0053] Based on the molar flow rates of each component at the first node and the basic step size, the molar flow rates of each component at the second node are determined by an integral solution method.

[0054] It is important to note that the first and second nodes are used only to indicate the order of the nodes; that is, the first node comes before the second node. The calculation of the first node is completed before the calculation of the second node.

[0055] In the embodiments of this specification, the molar flow rate of each component of the first node is calculated as follows:

[0056]

[0057] in,

[0058] F i,Z This represents the molar flow rate of component i at a step size Z;

[0059] r i，j This represents the reaction rate of component i in reaction j;

[0060] P represents total pressure;

[0061] Z represents the base step size;

[0062] T represents temperature.

[0063] In the embodiments described in this specification, r i，j The reaction rate of component i in reaction j is determined based on the reaction rate equations of important reactions involved in existing catalytic reforming reactions.

[0064] The aforementioned formula F i,Z The calculation process is as follows:

[0065] From reaction kinetics and the law of conservation of mass, we can obtain:

[0066]

[0067] r i,j =f i,j (F1,F2,…,F n (T,P,Z)

[0068] Thus obtain

[0069]

[0070] Table 2 shows the reaction rate equations for the important reactions involved in catalytic reforming.

[0071] Table 2

[0072]

[0073] Step S103: If there is a molar flow rate less than 0 in the molar flow rate of each component of the second node, then reduce the basic step size according to a preset ratio until the molar flow rate of each component of the second node is greater than 0.

[0074] In the embodiments described in this specification, the preset ratio is 0.5.

[0075] As mentioned earlier, after obtaining the molar flow rates of each component at the second node, it is necessary to further determine whether there are any molar flow rates less than 0 in the molar flow rates of each component at the second node. Because when the component flow rate is close to 0, integration calculations using the basic step size can easily result in the component composition being calculated as a duplicate, rendering the calculation results meaningless. Therefore, it is necessary to determine whether there are any molar flow rates less than 0 in the molar flow rates of each component at the second node.

[0076] In this embodiment of the specification, if there is a molar flow rate less than 0 in the molar flow rate of each component at the second node, the base step size is reduced by a preset ratio until the molar flow rate of each component at the second node is greater than 0. Specifically, this includes:

[0077] If there is a molar flow rate less than 0 in the molar flow rate of each component of the second node, then the basic step size is reduced to the first change step size according to a preset ratio.

[0078] Based on the first change step size and the molar flow rate of each component of the first node, the molar flow rate of each component of the new second node is obtained.

[0079] If the molar flow rate of each component at the new second node is greater than 0, then this calculation step is complete.

[0080] If there is a molar flow rate less than 0 in the molar flow rate of each component of the new second node, then the first change step size is reduced to the second change step size according to the preset ratio.

[0081] Based on the second change step size and the molar flow rate of each component at the first node, the calculation is completed when the molar flow rate of each component at the second node is greater than 0.

[0082] Step S105: Restore the reduced step size to the basic step size, and determine the molar flow rate of each component of the third node based on the molar flow rate of each component of the second node and the basic step size.

[0083] In the embodiments described in this specification, after calculating the molar flow rates of each component at the second node, calculating the molar flow rates of each component at the third node requires restoring the reduced step size to the basic step size. The molar flow rates of each component at the third node are then calculated using the basic step size and the molar flow rates of each component at the second node.

[0084] After obtaining the molar flow rates of each component at the third node, it is necessary to further determine whether there are any molar flow rates less than 0 among the molar flow rates of each component at the third node.

[0085] Step S107: Repeat the operation. If there is a molar flow rate of less than 0 for each component at the third node, reduce the basic step size according to the preset ratio until the molar flow rate of each component at each node of the plug flow reactor is calculated.

[0086] To further understand the reactor simulation method for catalytic reforming provided in the embodiments of this specification, Figure 2 This is a schematic diagram illustrating the calculation of determining a variable step size, provided as an embodiment of this specification. Figure 2 As shown, the dF of the first node A is calculated using a basic step size of 1. i / dZ, and then use

[0087]

[0088] Calculate F of the second node, i.e., point B. i F at point B i If the value is less than 0, the basic step size needs to be reduced to C, that is, point C is used as the new second node. At this time, point C needs to reduce the basic step size 1 to 0.5 according to the preset ratio of 0.5. The molar flow rate of each component at point C is calculated with 0.5 as the integration step size until the calculated molar flow rate is greater than or equal to 0.

[0089] In one embodiment of this specification, using a fixed-step algorithm to calculate a plug flow reactor requires reducing the basic step size to 0.001m and performing 470 calculations to obtain the result. However, using the variable-step algorithm provided in this embodiment, with a basic step size set to 0.0235m, the calculation can be completed in just 37 calculations.

[0090] To further understand the reactor simulation method in the embodiments of this specification, Figure 3 This is a framework diagram of a reactor simulation method for catalytic reforming provided for embodiments of this specification. Figure 3As shown, F is obtained according to the basic step size. i When, determine F i Does F have a value less than 0? i If the value is less than 0, the basic step size is reduced by a preset ratio until the obtained F value is reached. i ≥0. Then restore to the basic step size and calculate F for the next node. i .

[0091] Table 3 shows the feed and discharge results calculated by the method provided in the embodiments of this specification.

[0092] Table 3

[0093]

[0094]

[0095] As can be seen from Table 3, the method provided in this manual can yield good calculation results.

[0096] Table 4 is a schematic diagram of a calculation result provided in an embodiment of this specification.

[0097] Table 4

[0098]

[0099]

[0100] As can be seen from Table 4, the calculation requirements change with the step size, while ensuring that the amount of the main product remains stable.

[0101] Table 5 shows the results of a comparative experiment provided in the embodiments of this specification.

[0102] Table 5

[0103]

[0104]

[0105] As can be seen from Table 5, the method of this application has the same good effect as mature and effective products on the market.

[0106] The reactor simulation method provided in the embodiments of this specification can reduce the computational load of catalytic reforming reactions, and has fast calculation speed, good robustness, and high accuracy of calculation results.

[0107] The foregoing embodiments of this specification provide a reactor simulation method for catalytic reforming. Based on the same idea, the embodiments of this specification also provide a reactor simulation system for catalytic reforming. Figure 4This is a schematic diagram of a reactor simulation system for catalytic reforming provided in this illustrative embodiment.

[0108] like Figure 4 As shown, the reactor simulation system includes:

[0109] The first calculation module 401 determines the molar flow rate of each component in the second node based on the molar flow rate and basic step size of each component in the first node.

[0110] The variable step size calculation module 403, if there is a molar flow rate less than 0 in the molar flow rate of each component of the second node, then reduces the basic step size according to a preset ratio until the molar flow rate of each component of the second node is greater than 0.

[0111] The second calculation module 405 restores the reduced step size to the basic step size, and determines the molar flow rate of each component of the third node based on the molar flow rate of each component of the second node and the basic step size.

[0112] The circulation module 407 operates in a loop. If the molar flow rate of each component at the third node is less than 0, the basic step size is reduced according to the preset ratio until the molar flow rate of each component at each node of the plug flow reactor is calculated.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A reactor simulation method for catalytic reforming, characterized in that, The reactor simulation method includes: Based on the molar flow rate of each component at the first node and the basic step size, determine the molar flow rate of each component at the second node. If there is a molar flow rate less than 0 in any of the components of the second node, the basic step size is reduced by a preset ratio until the molar flow rate of each component of the second node is greater than 0. The reduced step size is restored to the basic step size, and the molar flow rate of each component in the third node is determined based on the molar flow rate of each component in the second node and the basic step size. The process is repeated. If any component at the third node has a molar flow rate less than 0, the base step size is reduced according to the preset ratio until the molar flow rate of each component at each node of the plug flow reactor is calculated.

2. The reactor simulation method as described in claim 1, characterized in that, The basic step length is determined based on the length of the plug flow reactor and the preset number of nodes.

3. The reactor simulation method as described in claim 1, characterized in that, The preset ratio is 0.

5.

4. The reactor simulation method as described in claim 1, characterized in that, If any molar flow rate of the components at the second node is less than 0, the base step size is reduced by a preset ratio until the molar flow rate of all components at the second node is greater than 0. Specifically, this includes: If there is a molar flow rate less than 0 in the molar flow rate of each component of the second node, then the base step size is reduced to the first change step size according to a preset ratio. Based on the first change step size and the molar flow rate of each component of the first node, the molar flow rate of each component of the new second node is obtained. If the molar flow rate of each component at the new second node is greater than 0, then this step of the calculation is complete. If there is a molar flow rate less than 0 in the molar flow rate of each component of the new second node, then the first change step size is reduced to the second change step size according to the preset ratio. Based on the second change step size and the molar flow rate of each component at the first node, the calculation is completed when the molar flow rate of each component at the second node is greater than 0.

5. The reactor simulation method as described in claim 1, characterized in that, The determination of the molar flow rate of each component at the second node based on the molar flow rate and basic step size of each component at the first node specifically includes: Based on the molar flow rates of each component at the first node and the basic step size, the molar flow rates of each component at the second node are determined by an integral solution method.

6. The reactor simulation method as described in claim 5, characterized in that, The molar flow rates of each component at the first node are calculated as follows: in, F i,Z This represents the molar flow rate of component i at a step size Z; r i，j This represents the reaction rate of component i in reaction j; P represents total pressure; Z represents the base step size; T represents temperature.

7. A reactor simulation system for catalytic reforming, characterized in that, The simulation system includes: The first calculation module determines the molar flow rate of each component in the second node based on the molar flow rate and basic step size of each component in the first node. The variable step size calculation module reduces the basic step size by a preset ratio if there is a molar flow rate less than 0 in the molar flow rate of each component in the second node, until the molar flow rate of each component in the second node is greater than 0. The second calculation module restores the reduced step size to the basic step size, and determines the molar flow rate of each component in the third node based on the molar flow rate of each component in the second node and the basic step size. The loop module operates in a loop. If the molar flow rate of each component at the third node is less than 0, the basic step size is reduced according to the preset ratio until the molar flow rate of each component at each node of the plug flow reactor is calculated.

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