CN-121980764-A - Multi-scale coupling modeling method for adiabatic axial fixed bed reactor

CN121980764ACN 121980764 ACN121980764 ACN 121980764ACN-121980764-A

Abstract

The invention discloses a multi-scale coupling modeling method of an adiabatic axial fixed bed reactor, which relates to the field of chemical process modeling and reaction engineering, and comprises the following steps of S1, constructing a three-level basic structure unit; S2, establishing a physical-chemical coupling calculation model, S3, embedding wide modulus parameter dynamic adaptation logic, S4, obtaining microscale reaction kinetic parameters, mesoscale transfer characteristic parameters and macro-scale equivalent performance parameters, S5, establishing a diffusion-reaction coupling equation of single catalyst particles to obtain comprehensive reaction-transfer parameters of particle scales, S6, establishing a macro-coupling model, describing a flow process in a reactor to realize trans-scale real-time coupling calculation of flow-diffusion-reaction-heat transfer, and S7, extracting the whole target performance parameters of the reactor based on the trans-scale real-time coupling calculation result. The method improves the prediction precision of the model, effectively serves for hot spot control and safe production of the reactor, and ensures the stability of industrial production.

Inventors

FAN XING
GU XIAONAN
HUA RUI
ZOU HAIXU
BAI XIANG
Ilchati. Delichati
Gulina Pidamaiti
WEI XIANYONG

Assignees

伊犁师范大学

Dates

Publication Date: 20260505
Application Date: 20251225

Claims (10)

1. The multi-scale coupling modeling method for the adiabatic axial fixed bed reactor is characterized by comprising the following steps of: S1, constructing three-level basic structure units of a microscale pore canal unit, a mesoscale agglomeration unit and a macro-scale particle unit based on the multistage structural characteristics of a catalyst and the requirement of a reaction system on a wide modulus range; S2, respectively establishing a physical-chemical coupling calculation model comprising diffusion, adsorption, desorption, chemical reaction and adiabatic heat transfer processes aiming at three-stage basic structure units; S3, embedding wide modulus parameter dynamic adaptation logic in the physical-chemical coupling calculation model, and dynamically matching and switching corresponding parameter functions according to the real-time modulus interval so as to maintain the continuity and accuracy of parameters in a wide modulus range; S4, carrying out numerical simulation based on the physical-chemical coupling calculation model to obtain microscale reaction kinetic parameters, mesoscale transfer characteristic parameters and macro-scale equivalent performance parameters; s5, establishing a diffusion-reaction coupling equation of the single catalyst particles, taking the mesoscale transfer characteristic parameter and the microscale reaction kinetic parameter as inputs, and obtaining the comprehensive reaction-transfer parameter of the particle scale through numerical solution; S6, establishing a macroscopic coupling model according to structural parameters of the reactor, describing the flow process in the reactor by adopting a computational fluid dynamics method, and combining wide modulus parameter dynamic adaptation logic and particle scale comprehensive reaction-transfer parameters to realize flow-diffusion-reaction-heat transfer cross-scale real-time coupling calculation; S7, extracting the overall target performance parameters of the reactor based on the trans-scale real-time coupling calculation result.
2. The method for modeling multi-scale coupling of adiabatic axial fixed bed reactor as claimed in claim 1, wherein in said step S3, said dynamic adaptation logic of wide modulus parameters comprises the steps of: S31, dividing the reaction rate modulus, the diffusion modulus and the heat transfer modulus into low, medium and high modulus sections respectively; s32, constructing a dedicated function relation of a reaction rate constant, an effective diffusion coefficient and an effective heat conduction coefficient aiming at different modulus intervals; s33, dynamically switching corresponding exclusive functions according to the modulus value obtained through real-time calculation, and enabling the parameters to smoothly transition in a wide modulus range.
3. The method for modeling the multi-scale coupling of the adiabatic axial fixed bed reactor according to claim 2, wherein the reaction rate modulus interval is divided into a low modulus interval [0.01,0.5], an intermediate modulus interval (0.5,10) and a high modulus interval (10, 100); the diffusion modulus interval is divided into a low modulus interval [0.1,1], an intermediate modulus interval (1, 10], a high modulus interval (10, 50]; the heat transfer modulus is divided into a low modulus region [0.05,1], an intermediate modulus region (1, 15), and a high modulus region (15, 80).
4. The method for modeling multi-scale coupling of an adiabatic axial fixed bed reactor as claimed in claim 1, wherein the effective diffusion coefficient D eff,micro of the micro-scale pore canal unit is obtained according to Bosanquet formula: Wherein D is Knudsen diffusion coefficient, and D is molecular diffusion coefficient.
5. The method for modeling multi-scale coupling of an adiabatic axial fixed bed reactor as claimed in claim 1, wherein the effective diffusion coefficient D eff,meso of the mesoscale agglomeration unit is modified according to the Bruggeman relation: ; Wherein D bulk is the bulk gas diffusion coefficient, ε meso is the aggregate void fraction, τ meso is the tortuosity.
6. The method for modeling multi-scale coupling of adiabatic axial fixed bed reactor as claimed in claim 1, wherein in step S5, the diffusion-reaction coupling equation of the single catalyst particles adopts a two-dimensional form in a spherical coordinate system, including radial and axial dimensions, and the source term of the equation is composed of microscale reaction dynamics and mesoscale transfer parameters.
7. The method for modeling multi-scale coupling of an adiabatic axial fixed bed reactor as defined in claim 1, wherein in the step S6, the macro-coupling model and the particle scale model are cooperatively solved by a bidirectional real-time coupling mechanism, and the method comprises the following steps: s61, taking the local flow velocity, the temperature and the component concentration of the macro-coupling model as boundary conditions of the particle scale model in each time step; s62, taking the reaction rate, the heat generation rate and the effective physical property parameters obtained by calculating the particle scale model as source items of a macroscopic model; And S63, completing parameter transmission and collaborative solving in each time step, and packaging data interaction by adopting a standardized format.
8. The method for modeling multi-scale coupling of an adiabatic axial fixed bed reactor as claimed in claim 1, wherein in the step S4, the numerical simulation is spatially discrete by adopting a finite volume method, the time advance is in a second-order implicit Crank-Nicolson format, the linear system solution is implemented by adopting a GMRES iterative algorithm and matched with ILU pretreatment, and a convergence residual threshold is set to be 1×10 -6 .
9. The method of modeling a multiscale coupling of an adiabatic axial fixed-bed reactor of claim 1, wherein in step S7, the target performance parameters include reactant conversion, product selectivity, bed temperature distribution, carbon deposition, and reactor pressure drop.
10. The method for modeling a multiscale coupling of an adiabatic axial fixed-bed reactor of claim 1, further comprising establishing a reaction mechanism network comprising a main reaction, a side reaction, and a carbon deposition reaction, wherein the kinetic parameters of each reaction path are independent of local temperature and key component concentration.

Description

Multi-scale coupling modeling method for adiabatic axial fixed bed reactor Technical Field The invention relates to the technical field of chemical process modeling and reaction engineering, in particular to a multi-scale coupling modeling method of an adiabatic axial fixed bed reactor. Background The adiabatic axial fixed bed reactor is widely applied to the catalytic reaction process in a plurality of industrial fields such as chemical industry, energy sources, environmental protection and the like by the characteristics of simple structure and stable operation. The reactors typically operate under adiabatic conditions with internal physicochemical processes spanning multiple levels of flow and heat transfer from the molecular scale reaction and diffusion within the micropores of the catalyst to mesoscale particle agglomeration transfer to macroscopic reactor scale, forming a typical and complex multiscale coupling system. In practical industrial production, the working condition of the reaction system is not constant, and the adjustment of the production load and the fluctuation of the quality of the raw materials can lead to the remarkable change of the reaction rate, the diffusion efficiency and the heat transfer effect, and the corresponding reaction rate modulus, the diffusion modulus and the heat transfer modulus can change within a very wide range. This wide modulus range of properties presents serious challenges for accurate modeling and simulation prediction of the reactor, and conventional modeling methods often have difficulty maintaining adequate accuracy and stability under such dynamic and wide operating conditions. For the multi-scale characteristics of adiabatic axial fixed bed reactors, various modeling methods have been developed in the prior art. These methods are generally directed to building a model framework from microscopic to macroscopic, approximating the overall behavior of the reactor by describing the physicochemical processes at different scales, respectively. When solving the multi-scale coupling problem, a common method is to preset or calibrate a set of fixed model parameters for a specific or narrower modulus operation interval, and unidirectionally transmit the parameters obtained by micro-scale calculation to a macroscopic model for use. This approach may have some effect in situations where the operating conditions are relatively fixed. However, the prior art solutions have significant drawbacks and disadvantages. Firstly, due to the lack of a dynamic adaptation mechanism for a wide modulus range, when the modulus exceeds a preset interval due to an actual working condition, model parameters cannot be accurately matched with a changed physicochemical process, so that the model prediction accuracy is seriously reduced. In the low modulus region, the law of parameter variation may be ignored, and in the high modulus region, numerical oscillation or result distortion may be caused by the lack of the parameter adaptation logic. In the transition region where the modulus interval is switched, discontinuous jump of the model parameters is often generated, which not only damages the consistency of trans-scale parameter transmission, but also can cause the problem that the numerical value solving process is difficult to converge, namely, the numerical value is unstable. Furthermore, the coupling between the conventional macroscopic model and the microscopic model is mostly simple unidirectional parameter transmission, bidirectional real-time collaborative solution cannot be realized, dynamic influence of reaction heat accumulation on microscopic reaction dynamics under adiabatic working conditions is difficult to capture and reflect, and real-time feedback of microscopic reaction change on a macroscopic flow field and a temperature field, namely scale coupling is not real-time. Accordingly, there is a need for an improvement over the deficiencies in the prior art to address the above-described issues. Disclosure of Invention The invention overcomes the defects of the prior art and provides a multi-scale coupling modeling method of an adiabatic axial fixed bed reactor. In order to achieve the purpose, the technical scheme adopted by the invention is that the invention provides a multi-scale coupling modeling method of an adiabatic axial fixed bed reactor, which comprises the following steps: S1, constructing three-level basic structure units of a microscale pore canal unit, a mesoscale agglomeration unit and a macro-scale particle unit based on the multistage structural characteristics of a catalyst and the requirement of a reaction system on a wide modulus range; S2, respectively establishing a physical-chemical coupling calculation model comprising diffusion, adsorption, desorption, chemical reaction and adiabatic heat transfer processes aiming at three-stage basic structure units; S3, embedding wide modulus parameter dynamic adaptation logic in the physical-chemical coupling