乙烯氧化反应器数学模拟

针对扬子石化公司乙烯氧化制环氧乙烷工业规模的壁冷式固定床反应器,在YS-6型银催化剂宏观动力学模型的基础上加以修正,获得了YS-7型银催化剂宏观动力学模型,建立了环氧乙烷合成固定床反应器的一维拟均相模型,通过模型计算值与工业生产实际值的比较,两者相差很小,验证了反应器模型和所用的宏观动力学模型的准确性,可用作扬子石化公司环氧乙烷合成反应器的模拟与操作优化。     

Mathematical simulation of an oilseed press

A mathematical model of an oilseed press was developed by superimposition of filtration analysis on screw extrusion theory to calculate press throughput and residual oil content in presscake for a given press geometry and physical properties of oilseed. The model predicted that press performance would improve, i.e., the throughput would increase and residual oil would decrease, if the press were cooled during operation. Longer presses would also give higher throughputs with lower residual oil contents. The predicted effects of changes in shaft speed and choke opening on press performance agreed reasonably well with experimental results obtained on a small laboratory press. A relatively large error of 9.0% in the prediction of throughput could be attributed to changes in viscosity of oilseed mass occurring during its passage through the press. It is expected that use of ‘expression’ analysis in place of the simple filtration analysis would improve the predictive ability of the model.     

半间歇搅拌釜式乙氧基化反应器的数学模拟

以KOH催化条件下乙二醇乙氧基化为例,建立了工业规模的、同时考虑动力学、气液平衡、气液传质、反应体积变化和惰性气体氮气影响等的半间歇搅拌釜式乙氧基化反应器的数学模型。通过数学模拟考察了环氧乙烷进料速率对反应器操作的影响,得到安全限制下适宜的环氧乙烷进料速率。在此基础上,模拟得到反应器中压力、环氧乙烷在气液相中的组成及乙氧基化产物随时间的分布,并同工业试验数据进行了比较。结果表明了模型的可靠性。     

Mathematical simulation of the combustion of slurry fuels

A mathematical model is proposed for the combustion of slurry fuels in the quasi-one-dimensional approximation. A numerical simulation is made of combustion of a slurry based on carbon and toluene in a combustion chamber and in a nozzle. The completeness of the combustion of the slurry is found to depend strongly on the excess oxidant ratio α_ox with maximum for α_ox ≈ 1. Scientific-Industrial Firm “State Institute of Applied Chemistry,” 197198 St. Petersburg. Translated from Fizika Goreniya i Vzyrva, Vol. 31, No. 6, pp. 41–48, November–December, 1995.     

Mathematical simulation of the hydrogenation of borodino coal

The kinetic and thermodynamic parameters of the hydrogenation of Borodino brown coal were calculated. With the use of equilibrium-kinetic analysis, the second-order reaction rate constants of forward and reverse reactions, the equilibrium constant, the activation energy, and the thermal effects of brown coal hydrogenation reactions were determined in a temperature range of 648–698 K at a hydrogen pressure of 10 MPa. In the course of the study, it was found that the experimental data are indicative of the adequacy of the equilibrium-kinetic analysis model for second-order reactions.     

Temperature and strain rate dependences of yield stress of polypropylene composites reinforced with carbon nanofibers

Polypropylene (PP) nanocomposites filled with 0.1, 0.3, 0.5, and 1.0 wt% carbon nanofiber (CNF) were prepared via melt compounding in a twin‐screw extruder followed by injection molding. The effects of CNF additions on the structure, mechanical and tensile yielding behavior of PP were investigated. TEM and SEM observations showed that CNFs were dispersed uniformly within PP matrix. Tensile test showed that the yield strength and Young's modulus of PP were improved considerably by adding very low CNF loadings. The reinforcing effect of CNF was also verified from the dynamic mechanical analysis. Impact measurement revealed that the CNF additions were beneficial to enhance the impact toughness of PP. The yield stress of the PP/CNF nanocomposites was found to be strain rate and temperature dependent. The yielding responses of PP/CNF nanocomposites can be described successfully by the Erying's equation and a reinforcing index n. The structure and mechanical property relationship of the nanocomposites is discussed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

石油黏度-温度数学模型研究

依据黏度的经验关联式,选用某石化公司催化原料及其馏分的性质数据,探讨了该馏分黏度与温度关系的数学模型,并利用非线性单纯形法进行回归计算,得到黏度-温度模型的相关经验常数。     

Mathematical simulation of the kinetics of visbreaking of tars

The results of the mathematical simulation of the thermal cracking (visbreaking) of tars are reported. The methods of plotting kinetic curves were proposed for the determination of visbreaking product concentrations in a reaction mixture under given conditions. The effectiveness of the algorithms of plotting kinetic curves on a computer with specified computational resources was compared.     

Mathematical simulation of the thermal stability of magnesium oxide

A simulation of the behavior of nonporous single-crystal magnesium oxide under conditions of heat loading that approach the operating conditions of casting ladles in ferrous metallurgy is performed by means of mathematical methods. Both numerical and analytic methods are used for the calculations. The temperature and mechanical stress fields and such breakdown parameters of materials as the moment of appearance of cracks, the thermal stability criterion (breakdown temperature drop of surface of material), etc. were determined as a result of the calculations. Results of calculations are presented and an analysis of the application of mathematical methods to the simulation of different heat treatment regimes of a material is performed.     

Mathematical simulation of the viscous properties of concentrated suspensions

A mathematical model for calculating the viscous properties of concentrated suspensions characterized by particle sizes of 30 to 800 µm), solids volume fractions of 1 to 70 vol %, different particle-size distributions, and a shear-rate range of 0.16 to 437 s^?1, which can describe the time evolution of the properties, is proposed. The model can be applied to calculating the viscous properties of catalyst oxide pastes, particulate-filled polymeric pastes, and the like.     

Mathematical simulation of wet spinning coagulation process: Dynamic modeling and numerical results

A dynamic model of polymer wet spinning coagulation process is proposed in this article. The model is based on the double diffusion phenomenon, phase separation process, continuity balance, and momentum balance of the entire coagulation process. The uniqueness of the model lies in its dynamic feature. The model can simulate the system's dynamic response to variations in system inputs/parameters. Steady‐state system solutions can also be produced as the long‐time solutions of the dynamic model; a settling time can be observed at the same time. This paper employs a computationally efficient method of lines numerical algorithm for solving the dynamic model. A simulation experiment on a selected non‐solvent‐solvent‐polymer ternary system is carried out to verify the model as well as the numerical method. The dynamic simulation results are analyzed and discussed. At the end of the article, h‐refinement and p‐refinement are used to confirm the spatial convergence of the numerical solutions. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3432–3440, 2016     

Mathematical modeling and simulation studies of scale-down fermentation systems

In this study, a scale-down approach has been used for the simulation of the imperfect mixing on the growth processes by considering several configurations of continuous stirred tank reactor (CSTR, aerated) and plug flow tubular reactor (PFTR, not aerated). The steady-state concentrations of biomass and enzyme in a continuous culture were calculated as a function of dilution rate using modified Monod growth kinetics. A mathematical model for each combination of two bioreactors was developed to account for growth, substrate utilization (oxygen and glucose) and enzyme synthesis and decay. The model was then used to investigate biomass production and enzyme expression in relation to the volumetric fraction U_f = V_PFTR /(V_CSTR + V_PFTR ) and the recirculation ratio R = f_r/(f + f_r) of the fermentation system. These two mixing parameters were found to be significant factors in the biomass and enzyme production from the fermentation system. This model was also compared with some of the existing models.     

Mathematical simulation of bioseparation in an affinity packed column

Affinity chromatography (biospecific adsorption) relies on specific interactions of biological molecules such as enzymes, antigens, antibodies, and proteins. The process consists of three steps: adsorption, washing, and elution. A mathematical model including convection, diffusion, and reversible reaction is formulated to analyse the breakthrough behaviour of the solute. A moving finite element orthogonal collocation method is applied with respect to the space variables of the governing partial differential equations of the model to evaluate the breakthrough of the solute. Danckwerts' boundary conditions are considered for the column. The validity of the numerical scheme is checked by comparison with an analytical solution for a simplified model. The results obtained from model simulation show that the breakthrough time of the solute is significantly influenced by the axial dispersion coefficient, solute concentration, ligand content, reaction kinetics, particle porosity, particle size, and flow rate. Solute recovery and bed utilisation efficiencies are evaluated for different values of the above parameters.     

分子蒸馏过程数学建模及模拟验证

建立了分子蒸馏过程径向和轴向的二维数学模型,采用CFD方法对DBP-DBS混合物系的分离过程进行模拟计算,分析了蒸馏温度和进料速率等操作条件对蒸馏过程的影响。将模拟结果与文献中采用BGK模型计算得到的结果进行对比,两者具有较好的吻合性,验证了模型的合理性。     

Mathematical simulation of granulation process in a speed granulator

The results of theoretical and experimental investigations of particles agglomeration in a speed granulator accompanied by the break-up of particles have been presented. The dependences that make it possible to estimate the contribution of agglomeration and break-up during the formation of granules from powder particles and to determine the average weight of particle on the apparatus outlet have been proposed.     

Mathematical simulation of mechanochemical synthesis in a macroscopic approximation

Physical theory of mechanochemical synthesis and its mathematical model in a macroscopic approximation are developed. The model is analyzed using analytic methods. The synthesis in a pre-activated system (two-stage synthesis) and in a reactor with mechanical reaction activation (one-stage synthesis) is studied. Relations determining the characteristics of the process are obtained. The accuracy of the analytical estimates is tested by numerical simulation.     

焦炉直行温度数学模型

建立了以一组燃烧室为对象的焦炉直行温度数学模型 ,以仿真推焦计划等因素对焦炉直行温度的影响,为焦炉直行温度的优化设定提供了理论依据。     

Temperature dependences of density of sodium borosilicate glasses in equilibrium states at temperatures below a vitrification temperature

The temperature dependences of the density and intensity of SAXRS of a variety of sodium borosilicate glasses in equilibrium states below vitrification temperature are obtained. The existence of a transition of the investigated supercooled liquids in a solid noncrystalline state was discovered that is similar to the one observed in the study of vitreous boron oxide and alkali-borate glasses. The temperature of the transition of supercooled liquids of the investigated compositions to a solid noncrystalline state is about 50°C below the vitrification temperatures determined by the SAXRS data. Thus, the transition occurs at a viscosity of 1014 P in borate and sodium borosilicate glasses.