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    • 专利摘要:
    The present invention discloses a resistance calculation method for theSCR denitrification catalyst, and belongs to the field of computer—aided engineering technology. The present invention includes the following steps: constructing a mesoscopic three—dimensional model of the SCR denitrification catalyst; meshing the mesoscopic model; analyzing the meshed model to obtain the resistance value of the SCR denitrification catalyst in a mesoscopic condition; fitting the obtained resistance value to obtain the resistance calculation formula of the SCR denitrification catalyst; constructing a macroscopic model of the SCR denitrification catalyst, and obtaining the inertial resistance coefficient and the viscous resistance coefficient based on the resistance formula obtained through fitting; and performing numerical simulation analysis based on the macroscopic model to obtain a resistance value of the SCR denitrification catalyst. In the present invention, multi—scale numerical simulation in Which macroscopic and mesoscopic are combined is applied to the SCR denitrification catalyst, Which reduces consumption of computer resources and improves calculation efficiency. Applicant 1: Anhui University of Technology Applicant 2: Anhui Vectra Environmental Protection Technology Co., Ltd.
    公开号:NL2025756A
    申请号:NL2025756
    申请日:2020-06-04
    公开日:2020-12-11
    发明作者:Qian Fuping；Wang Laiyong；Zhu Jingjing；Huang Naijin；Wu Hao
    申请人:Univ Anhui Technology；Anhui Weida Environmental Tech Co Ltd；
    IPC主号:
    专利说明:

    1 AO 20.06.1081 NLRESISTANCE CALCULATION METHOD FOR SCR DENITRIFICATIONCATALYST
    TECHNICAL FIELD The present invention relates to the field of computer-aided engineering technology, specifically to a resistance calculation method for a catalyst, and more specifically, to a CFD-based numerical simulation method in which macroscopic and mesoscopic are combined.
    BACKGROUND A selective catalytic reduction (SCR) flue gas denitrification system can become a basic flue gas denitrification technology in China in the long run because of its high denitrification efficiency, low ammonia escape rate, easiness in operation, and safety. Currently, many scholars at home and abroad have studied the resistance of a unidirectional fluid in a porous medium channel, and proposed corresponding revisions to a resistance calculation formula. However, there are still some differences and disadvantages in conclusions drawn. So far, in the porous medium channel, there is still no universal resistance calculation formula for fluid flow, and the calculation method is still controversial.
    In recent years, with the development of computer-aided engineering technology, computational fluid dynamics (CFD) has been widely applied. Flow can be simulated by using related software to obtain various types of information, such as a velocity and pressure distribution, about a flow field, and therefore resistance information can be further obtained. Currently, in most studies on calculating the resistance of the SCR denitrification by using the CFD, a mesoscopic model of the catalyst is constructed for numerical simulation calculation. However, this method involves a large calculation amount and low calculation efficiency. In a few studies, an internal structure of the catalyst is simplified as a porous medium model for numerical simulation. However, this method involves a relatively large calculation error. In addition, the CFD consumes excessive labor and computer resources, and therefore it is still difficult to apply the CFD to a complex device.
    2 AO 20.06.1081 NL So far, for studies on resistance characteristics of porous media, there are many related literatures published, but most literatures provide only experimental results and qualitative analysis. In addition, due to limitations of experimental conditions of researchers, experimental conclusions differ greatly from each other, and there are still many theoretical studies.
    Patent publication No. CN 107462280A entitled "WEAR AND CLOGGING DIAGNOSTIC METHOD FOR SCR DENITRIFICATION CATALYST" is retrieved. The diagnostic method of this application includes: illustrating and marking wear and clogging statuses of a catalyst inside a reactor, and drawing a visual cloud picture; sampling the catalyst inside the reactor, and testing and analyzing mechanical properties of the catalyst to obtain test and analysis data of the catalyst; performing field test on a denitrification device to obtain actual flow field operation data of the denitrification device; constructing, through CFD numerical simulation and physical model test, a model that is consistent with a structure of the catalyst and an internal structure of the reactor; and obtaining wear and clogging causes for the catalyst with reference to the visual cloud picture, the data, and the model. In this application, service life of the catalyst is prolonged, and the risk of an operation accident of the denitrification device is reduced. However, this application still involves a large calculation amount and calculation accuracy is to be improved, and therefore needs to be further improved.SUMMARY
    1. Technical problems to be resolved in the present invention. The present invention is intended to solve problems of a large calculation amount, low calculation efficiency, and a relatively large calculation error in current calculation of the resistance of a denitrification catalyst, and provides a resistance calculation method for SCR denitrification catalyst. In the present invention, a mesoscopic model of the denitrification catalyst is constructed; a resistance value of the SCR denitrification catalyst in a mesoscopic condition is obtained by changing the height, porosity, and the inlet flow rate of the catalyst; the resistance value is fitted to obtain a resistance calculation formula of the denitrification catalyst; and a macroscopic model of the catalyst is constructed, and complex and small-scale structures of the catalyst are
    3 AO 20.06.1081 NL simplified as porous media. The number of meshes is greatly reduced when the macroscopic porous medium model is meshed. In this way, the calculation amount is reduced, calculation accuracy is improved, and guidance on catalyst selection can be provided.
    2. Technical solutions To achieve the foregoing objective, the technical solutions provided in the present invention are as follows: A resistance calculation method for the SCR denitrification catalyst according to the present invention includes the following steps: step 1: constructing a mesoscopic three-dimensional geometric model of the SCR denitrification catalyst; step 2: meshing the obtained mesoscopic model of the SCR denitrification catalyst; step 3: analyzing the meshed model to obtain the resistance value of the SCR denitrification catalyst in a mesoscopic condition; step 4: fitting the obtained resistance value to obtain the resistance calculation formula of the SCR denitrification catalyst; step 5: constructing a macroscopic model of the SCR denitrification catalyst, and obtaining the inertial resistance coefficient and the viscous resistance coefficient based on the resistance formula obtained through fitting; and step 6: performing numerical simulation analysis based on the macroscopic model to obtain the resistance value of the SCR denitrification catalyst. Further, in step 3, the meshed model is analyzed based on CFD software, and the resistance value of the SCR denitrification catalyst in the mesoscopic condition is obtained by changing the height, porosity, and the inlet flow rate of the SCR denitrification catalyst. Further, in step 3, 16 denitrification catalyst models are constructed with random combinations of four catalyst heights and four types of catalyst porosity, and resistance values of the SCR denitrification catalyst in the mesoscopic condition at different flow rates are obtained by changing inlet flow rates of the 16 denitrification catalyst models.
    4 AO 20.06.1081 NL Further, in step 3, the four catalyst heights constructed are 200 mm, 400 mm, 600 mm, and 800 mm; the four types of catalyst porosity are 0.746, 0.736, 0.728, and (0.723; and values of the inlet flow rates are 1 m/s, 2 m/s, 3 m/s, 4 m/s, and 5 m/s. Further, in step 4, data fitting is performed by using an Ergun equation: Ap (l-e) 1-£) L ade de ‚ where Ap represents the resistance value, L represents the thickness of the catalyst, d represents the diameter of an open pore of the catalyst, ¢ represents the porosity of the catalyst, p represents density of air, & represents dynamic viscosity of the air, v represents a gas flow rate in the catalyst, and A and B represent fitting coefficients. Further, a semi-empirical formula obtained in step 4 for calculating the resistance of the SCR denitrification catalyst in the mesoscopic condition is as follows: A I-e}) 1-€) 20 237321300280 Lv +0.03206 9) pv L de de’ i Further, internal structures of the catalyst are all simplified as porous media when the macroscopic model of the catalyst Is constructed. Further, in step 5, the inertial resistance coefficient and the viscous resistance coefficient in the porous medium model are obtained based on the resistance calculation formula obtained through fitting and with reference to a momentum conservation equation: a d’ el Cc = 906592 (1-8) : d e where d represents the diameter of the open pore of the catalyst, € represents the porosity of the catalyst, //a represents the viscous resistance coefficient of the porous medium, and C: represents the inertial resistance coefficient of the porous medium.
    3. Beneficial effects
    AO 20.06.1081 NL Compared with known technologies, the technical solutions provided in the present invention have the following significant effects: (1) In the resistance calculation method for the SCR denitrification catalyst according to the present invention, The mesoscopic geometric model of the catalyst is constructed 5 using the multi-scale numerical simulation method in which macroscopic and mesoscopic are combined; by changing the operating parameter of the denitrification catalyst, a resistance change caused by airflow passing through the catalyst can be obtained through simulation; formula fitting is performed by using the foregoing data to obtain the resistance calculation formula of the catalyst; the inertial resistance coefficient and the viscous resistance coefficient required for simulation of the porous medium are obtained by using the formula; and then numerical simulation of the macroscopic porous medium is performed. In this way, the obtained numerical simulation result has high accuracy.
    (2) In the resistance calculation method for the SCR denitrification catalyst according to the present invention, the resistance calculation formula is obtained by fitting the result of mesoscopic numerical simulation, the related parameters required for macroscopic numerical simulation are deduced, and the Ergun equation is revised based on the mesoscopic model, to obtain a transfer relationship between macroscopic data and mesoscopic data of the catalyst, which ensures accuracy of the obtained result.
    (3) In the resistance calculation method for the SCR denitrification catalyst according to the present invention, the complex and small-scale structures of the denitrification catalyst are simplified as porous media, and the number of meshes is significantly reduced during meshing. In this way, resource consumption is greatly reduced, and calculation efficiency is improved.
    BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a flowchart of a CFD-based resistance calculation method for the SCR denitrification catalyst according to the present invention; FIG. 2 is a diagram of geometric model of the catalyst constructed at a mesoscopic level according to the present invention; FIG. 3 is a diagram of porous medium of the catalyst constructed at a macroscopic level according to the present invention; and
    6 AO 20.06.1081 NL FIG. 4 is a graph of formula fitting by using the resistance value according to the present invention. Reference numerals in the diagram:
    1. Outer wall of a mesoscopic catalyst; 2. Inner wall between channels of the mesoscopic catalyst; 3. Channel of the mesoscopic catalyst.
    DESCRIPTION OF EMBODIMENTS To further understand content of the present invention, the present invention is described in detail with reference to the accompanying drawings and embodiments.
    Embodiment 1 An SCR denitrification system of a large coking plant is used as an example. Internal devices of the SCR denitrification system are relatively complex, it is relatively difficult to predict uniformity of airflow distribution, the catalyst is an important part of the denitrification system, and it is particularly important to accurately measure a resistance change caused by a catalyst layer. With reference to FIG. 1, the resistance calculation method for the SCR denitrification catalyst in this embodiment, multi-scale numerical simulation in which macroscopic and mesoscopic are combined is performed on the SCR denitrification catalyst based on CFD software, to calculate the resistance change caused by fluid passing through the catalyst layer. The resistance calculation method includes the following steps. Step 1: Construct a mesoscopic three-dimensional geometric model of the SCR denitrification catalyst, where specific parameters such as the height, the width, the number of open pores, and the diameter of the open pore of the catalyst are set based on the actual size of the catalyst used in engineering. Step 2: Mesh the mesoscopic model. A specific process is as follows: The mesoscopic three-dimensional model of the denitrification catalyst is imported into CFD preprocessing software to divide the model into several parts, meshing density is set based on the sizes of different parts, mesh encryption processing is performed on the part of the model with a relatively complex structure, and mesh parameters are checked
    7 AO 20.06.1081 NL and adjusted, so that overall mesh quality of the model is above 0.3. Step 3: Analyze the meshed model based on CFD software. A boundary condition used for simulation is a velocity inlet and a pressure outlet (relative pressure at the outlet is p=0 Pa), and a wall is processed based on a standard wall function, and there is a no- slip boundary condition on the wall. The resistance value of the SCR denitrification catalyst in a mesoscopic condition is obtained by changing the height, porosity, and the inlet flow rate of the SCR denitrification catalyst. Specifically, 16 denitrification catalyst models are constructed with four heights (200 mm, 400 mm, 600 mm, and 800 mm) and four types of porosity (0.746, 0.736, 0.728, and 0.723), and resistance values of the SCR denitrification catalyst in the mesoscopic condition at inlet flow rates 1 m/s, 2 m/s, 3 m/s, 4 m/s, and 5 m/s are obtained by changing inlet flow rates of the 16 catalyst models.
    Step 4: Perform polynomial fitting on the obtained resistance value of the catalyst in the mesoscopic condition, and compare the fitting result with the calculation result of a related resistance calculation formula. It is learned that an Ergun equation has the same trend as a simulation result, and therefore data fitting is performed by using this equation. The Ergun equation is as follows: ap ale Ie L de’ de’ ‚ where Ap represents the resistance value, L represents the thickness of the catalyst, d represents the diameter of an open pore of the catalyst, & represents the porosity of the catalyst, p represents density of air, & represents dynamic viscosity of the air, v represents a gas flow rate in the catalyst, and A and B represent fitting coefficients.
    Further, a semi-empirical formula for calculating the resistance of the SCR denitrification catalyst in the mesoscopic condition is obtained as follows: 2 aL 2873213026) Lv 003296 122) pv’ L de de’ ‚ where e=1-Vs/V, V represents a total volume of a catalyst region, and V, represents a total volume of a solid catalyst.
    8 AO 20.06.1081 NL Step 5: Construct a macroscopic porous medium model of the SCR denitrification catalyst, and obtain the inertial resistance coefficient and the viscous resistance coefficient in the porous medium model based on the resistance calculation formula obtained through fitting and a momentum conservation equation.
    A specific process is as follows: The macroscopic model is constructed based on the actual external size of the catalyst, and complex structures {inner wall and channel) with a small size of the catalyst are simplified as porous media.
    The resistance calculation formula of the SCR denitrification catalyst obtained through fitting: 2 = 287.321 ol) + 0.032068) pr and the momentum conservation equation: S, = 4 v, +C, Lol 3 a 2 are simplified and integrated, to obtain an expression of viscous resistance coefficients in all directions of the porous medium: 1_287.3213 (l-e) a d €) and an expression of inertial resistance coefficients in all the directions of the porous medium: € 006592 (1-¢) : d e where d represents the diameter of the open pore of the catalyst, £ represents the porosity of the catalyst, //o represents the viscous resistance coefficient of the porous medium, and C; represents the inertial resistance coefficient of the porous medium.
    Step 6: Perform numerical simulation analysis based on the macroscopic porous medium model by using the CFD software to obtain the resistance value of the SCR denitrification catalyst.
    A specific process is as follows: The macroscopic porous medium model of the catalyst is meshed, mesh parameters are checked and adjusted, so that overall mesh quality of the model is above 0.3, and then Fluent software is imported for numerical simulation.
    The boundary condition of the catalyst required for numerical simulation is the velocity inlet and the pressure outlet (relative pressure at the
    9 AO 20.06.1081 NL outlet is p=0 Pa), and a wall is processed based on a standard wall function, and there is a no-slip boundary condition. Then, the inertial resistance coefficient and the viscous resistance coefficient in the porous medium model are input. Finally, numerical simulation analysis is performed and the macroscopic simulation resistance value of the denitrification catalyst is obtained.
    The macroscopic simulation result is compared with an experimental result, and it is learned that the two results are consistent in trend. In addition, the maximum error between the simulation value and the experimental value (the experimental value is measured by placing a resistance measurement apparatus at both ends of a catalyst inlet and a catalyst outlet in the engineering field) of the resistance of the catalyst in a macroscopic condition is 8.6%. The conclusion drawn in this embodiment is consistent with the trend of the experimental value, which proves correctness of the CFD-based multi-scale numerical simulation method in which macroscopic and mesoscopic are combined for a denitrification catalyst and that is used in this embodiment. In this embodiment, the multi-scale numerical simulation method in which macroscopic and mesoscopic are combined 1s used. FIG. 2 shows the constructed mesoscopic geometric model of the catalyst. In FIG. 2, reference numeral 1 indicates an outer wall of the mesoscopic catalyst, reference numeral 2 indicates an inner wall between channels of the mesoscopic catalyst, and reference numeral 3 indicates a channel of the mesoscopic catalyst. By changing an operating parameter of the denitrification catalyst, the resistance change caused by airflow passing through the catalyst can be obtained through simulation. As shown in FIG. 4, formula fitting is performed by using the foregoing data to obtain the resistance calculation formula of the catalyst; the inertial resistance coefficient and the viscous resistance coefficient required for simulation of the porous medium are obtained by using the formula; and then numerical simulation of the macroscopic porous medium shown in FIG. 3 is performed, and the resistance value obtained in the numerical simulation result is compared with the experimental result. In this way, accuracy of numerical simulation is verified, correctness of the resistance calculation formula of the SCR denitrification catalyst is shown, and the transfer relationship between macroscopic and mesoscopic data of the catalyst is obtained.
    10 AO 20.06.1081 NL It is worth to note that the Ergun equation is most widely used in several commonly used resistance prediction models at present. However, in the Ergun equation, only porosity and a particle diameter are used to represent impact of the geometry of a porous medium channel on flow characteristics. There are different pore structures (such as a catalyst honeycomb structure and a ceramic foam structure) in practice, and when these structures are simplified as porous media, direct use of the Ergun equation can cause a large error. Based on this, the Ergun equation is revised based on the mesoscopic model in this embodiment, to establish the multi-scale data transfer relationship, which ensures accuracy of the obtained result.
    In addition, in the conventional resistance calculation method, modeling is usually directly performed by using a device and then calculation is performed. Therefore, a large quantity of computational meshes need to be used for complex structures and small-scale structures. In this case, results usually have lower calculation accuracy, and higher requirements are imposed on computers. In this embodiment, multi-scale numerical simulation in which macroscopic and mesoscopic are combined is applied to the SCR denitrification catalyst. Because the complex and small-scale structures of the denitrification catalyst are simplified as porous media, the number of meshes is significantly reduced during meshing. In this way, resource consumption is greatly reduced, and calculation efficiency is improved. The present invention and implementations thereof are schematically described above, and the description constitutes no limitation. The accompanying drawings merely show one of the implementations of the present invention, and an actual structure is not limited thereto. Therefore, a structure mode and an embodiment that are similar to the technical solution and that are designed, without departing from the creative objective of the present invention and creativity, by a person of ordinary skill in the art inspired by the present invention shall fall within the protection scope of the present invention.
    权利要求:
    Claims (1)
    [1]
    A resistance calculation method for the SCR denitrification catalyst, comprising the steps of: step 1: constructing a mesoscopic three-dimensional geometric model of the SCR denitrification catalyst; step 2: refining the obtained mesoscopic model of the SCR denitrification catalyst; step 3: analyzing the fine-mesh model to obtain the resistance value of the SCR denitrification catalyst in a mesoscopic state; step 4: adjusting the obtained resistance value to obtain the formula for calculating the resistance of the SCR denitrification catalyst; step 5: constructing a macroscopic model of the SCR denitrification catalyst and obtaining the inertia coefficient and the viscous drag coefficient based on the drag formula obtained by adjustment; and step 6: performing numerical simulation analysis based on the macroscopic model to obtain the resistance value of the SCR denitrification catalyst.
    Resistance calculation method for the SCR denitrification catalyst according to claim 1, wherein in step 3 the fine-mesh model is analyzed based on CFD software, and the resistance value of the SCR denitrification catalyst in mesoscopic state is obtained by changing the height, porosity and inlet flow rate of the SCR dent trification catalyst.
    Resistance calculation method for the SCR denitrification catalyst according to claim 2, wherein in step 3 16 denitrification catalyst models are constructed with arbitrary combinations of four catalyst heights and four types of catalyst porosity, and resistance values of the SCR denitrification catalyst in the mesoscopic state at different flow rates are obtained by the inlet change flow rates of the 16 denitrification catalyst models.
    12 AO 20.06.1081 NL
    The method of calculating the resistance for the SCR denitrification catalyst according to claim 3, wherein in step 3 the four constructed catalyst heights are 200 mm, 400 mm, 600 mm and 800 mm; the four types of catalyst porosity are 0.746, 0.736, 0.728 and 0.723; and values of the inlet flow rates are 1 m / s, 2 m / s, 3 m / s, 4 m / s and 5 m / s.
    5. Resistance calculation method for the SCR denitrification catalyst according to claim 4, wherein in step 4 the adjustment of data is carried out using an Ergun equation: A 1-e}) Ig Ee pl €) 2 L d'e de, where Ap stands for the resistance value, L stands for the thickness of the catalyst, d stands for the diameter of an open pore of the catalyst, ¢ stands for the porosity of the catalyst, p stands for air density, & stands for dynamic viscosity of the catalyst, v represents a gas flow rate in the catalyst, and A and B represent adjustment coefficients.
    The method of calculating the resistance for the SCR denitrification catalyst according to claim 5, wherein a semi-empirical formula obtained in step 4 for calculating the resistance of the SCR denitrification catalyst in the mesoscopic state is as follows: Ap 1- ¢) le 237321301220 w + 0.03206 =%) pv L the de
    Resistance calculation method for the SCR denitrification catalyst according to claim 5 or 6, wherein internal structures of the catalyst are all simplified as porous media when constructing the macroscopic model of the catalyst.
    8. The method of calculating the resistance for the SCR denitrification catalyst according to claim 7, wherein in step 5 the inertia coefficient
    13 AO 20.06.1081 NL and the viscous drag coefficient in the porous medium model are obtained from the drag calculation formula obtained by adjustment and with reference to an equation of conservation of momentum:
    1 287.3213 (1-0) c = 006592 (9)) d €, where d is the diameter of the open pore of the catalyst, & is the porosity of the catalyst, J / a is the viscous drag coefficient of the porous medium and C; represents the inertia coefficient of the porous medium.
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    同族专利:
    公开号 | 公开日
    NL2025756B1|2020-12-17|
    CN110210137A|2019-09-06|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
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    CN112100891A|2020-09-15|2020-12-18|安徽工业大学|CFD-based resistance calculation method for porous medium in dust holding state|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    CN201910484081.XA|CN110210137A|2019-06-05|2019-06-05|A kind of drag computation method of SCR denitration|
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