跨越精馏单元边界分离的可行性研究

提出了判断跨越精馏单元边界分离的可行性的图像法。这种方法根据组分的挥发度分析精馏段和提馏段组成变化,从而判断分离的可行性。等挥发度曲线和挥发度顺序图被用来分析各组分挥发度的变化。结果表明,跨越精馏单元边界的分离只能从一个方向进行,可行的方向与等挥发度曲线有关。此外,利用Aspen P lus对三组分共沸系统中跨越精馏单元边界的分离进行了模拟,模拟结果与用相对挥发度顺序图分析的结果一致。     

Multi-physics analysis on a unimorphic piezoelectric diaphragm according to its shape and boundary conditions for the performance enhancement

A micro-viscometer for measuring viscosity change in small amount of liquid in real time has been proposed recently. The advantages of the device are the use of minimal liquid and maximized sensitivity for measuring viscosity. However, in previous research, even though the multi-physical simulation including electrical, mechanical, and acoustical phenomenon is necessary for design of micro-viscometer, only acoustical aspects have been considered. Thus, combined physical phenomena could not be reflected for an optimum design process. In this research, a multi-physical approach is developed for designing a micro-viscometer, and an optimized micro-viscometer design is proposed. The proposed method is able to capture multi-physical phenomena such as near field effect and added mass effect. It also has the advantage of flexible design of various shape and materials, leading to savings of cost and time.     

On the feasibility and reliability of nonlinear kinetic parameter estimation for a multi-component photocatalytic process

Nonlinear kinetic parameter estimation plays an essential role in kinetic study in reaction engineering. In the present study, the feasibility and reliability of the simultaneous parameter estimation problem is investigated for a multi-component photocatalytic process. The kinetic model is given by the L-H equation, and the estimation problem is solved by a hybrid genetic-simplex optimization method. Here, the genetic algorithm is applied to find out, roughly, the location of the global optimal point, and the simplex algorithm is subsequently adopted for accurate convergence. In applying this technique to a real system and analyzing its reliability, it is shown that this approach results in a reliable estimation for a rather wide range of parameter value, and that all parameters can be estimated simultaneously. Using this approach, one can estimate kinetic parameters for all components from data measured in only one time experiment.     

On the feasibility of the microscale approach for a multistep biotransformation: sitosterol side chain cleavage

BACKGROUND: The millilitre/microlitre‐scale approach is widely used for screening purposes and one‐pot biotransformations, but it has seldom been applied to whole cell multistep biotransformations and two‐liquid biphasic processes. The present study aims to contribute to filling this gap by using 24‐well microtitre plates as reactors for the side chain cleavage of sitosterol with resting cells of Mycobacterium sp. NRRL B‐3805 and comparing results with other set‐ups. RESULTS: High catalytic activity in microtitre plates and aqueous medium was observed at 250 rpm shaking frequency and 25 mm shaking diameter with 80% headspace and a mixture of Mg²⁺, Zn²⁺, Mn²⁺ and Co²⁺ salts. Data obtained with microtitre plates were reproduced in other set‐ups when aqueous medium was used, whereas higher biotransformation rates were recorded in stirred reactors when biphasic systems were employed. CONCLUSION: Results suggest that microtitre plates may be used for the characterisation of complex bioconversion systems to establish representative screening systems, particularly if based in aqueous phase systems. Probing experiments also demonstrated the feasibility of using microlitre/millilitre shaken bioreactors to evaluate organic/aqueous two‐liquid bioconversion systems, although the enhanced mass transfer patterns resulting from the biphasic system hampered the translation of the data to the more common stirred reactor configuration. Copyright © 2007 Society of Chemical Industry     

燃气压缩机组油冲洗技术

以国家重点工程——西气东输增输工程古浪增压站压缩机组油冲洗为例,重点阐述了燃气压缩机组油系统冲洗的技术关键,提出了油冲洗具备的条件、管路清洁、油冲洗温度控制、检验标准及管路恢复的一些可供借鉴的方法。     

On the quantification of the controlling regimes in automotive catalytic converters

The conversion of pollutants in automotive catalytic converters is influenced by a number of physical and chemical processes that take place in the gaseous and solid phases as the exhaust gases flow through the converter. A detailed understanding of the complex processes involving flow dynamics, heat and mass transport and heterogeneous surface reactions is of crucial importance to improve the converter design. The main objective of the present study is to quantify the magnitudes of the external and internal mass transfer as well as chemical reaction limiting processes as a function of the converter operating temperature. To this end, experimental data, obtained for a three way catalyst (TWC) under real world operating conditions, are analyzed and compared against analytical expressions that allow for the quantification of the different limiting processes involved. The results demonstrate that (i) the external mass transfer resistance overlaps the reaction resistance only at moderate operating temperatures and not immediately above the ignition temperature as generally considered in the literature, (ii) the transport phenomena (external and internal mass transfer) represents 90% of the total resistance for temperatures higher than 792 K, (iii) the internal mass transfer in the porous washcoat presents a larger resistance than the external mass transfer from the bulk fluid to the washcoat wall even at high operating temperatures, and (iv) based on the quantification of the individual resistances as a function of the TWC operating temperature, it was demonstrated both the influence of the substrate cell density and of the effective diffusivity on the TWC conversions. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

On the use of choking as a boundary for fast fluidizationsimulation of counter-diffusional mass transfer

Fast fluidization is widely regarded as a flow regime between the dilute and dense-phase transport regimes in upward flow of gas-particle suspensions where choking does not occur and the system is insensitive to changes in superficial gas velocity and solids flux. Among the attempts in recent years to predict the boundaries of the fast fluidization regime, the use of the concept of choking appears to be most popular. This paper examines the validity of the use of choking as a boundary for fast fluidization. It is shown that this approach arises from the confusion in the definition of choking. Alternative methods are discussed which would enablebetter prediction of the boundaries of fast fluidization.     

转化器新型冷却剂的应用

分析了正庚烷代替热水作为氯乙烯转化器反应冷却剂的优势,介绍了用正庚烷作为冷却剂的工艺流程和运行情况。     

On the derivation of graphically inspired feasibility constraints for distillation network synthesis

We propose the integration of simplified graphically inspired feasibility constraints into optimization-based models for distillation network synthesis. The approach facilitates the use of surrogate, potentially data-based, distillation column models while considering feasibility in a computationally efficient manner. The proposed approach can aid the formulation of efficient approaches for preliminary distillation network synthesis.     

A level set based immersed boundary method for simulation of non-isothermal viscoelastic melt filling process

In this work, the polymer melt filling process is simulated by using a coupled finite volume and level-set based immersed boundary (LS-IB) method. Firstly, based on a shape level set (LS) function to represent the mold boundary, a LS-IB method is developed to model the complex mold walls. Then the non-isothermal melt filling process is simulated based on non-Newtonian viscoelastic equations with differ-ent Reynolds numbers in a circular cavity with a solid core, and the effects of Reynolds number on the flow patterns of polymer melt are presented and compared with each other. And then for a true polymer melt with a small Reynolds number that varies with melt viscosity, the moving interface, the temperature distributions and the molecular deformation are shown and analyzed in detail. At last, as a commonly used application case, a socket cavity with seven inserts is investigated. The corresponding physical quantities, such as the melt velocity, molecular deformation, normal stresses, first normal stress differ-ence, temperature distributions and frozen layer are analyzed and discussed. The results could provide some predictions and guidance for the polymer processing industry.     

On shape normalization for non-uniformly active catalyst pellets

The possibility of shape normalization of catalyst pellets with non-uniform catalytic activity profiles is examined. A first order isothermal reaction occurring in slab or spherical catalyst pellets, with a variety of activity profiles, is considered. Analytic solutions for the effectiveness factor are reported in all cases. When the catalytic activity at the external surface of the pellet is non-zero, a physically significant normalization of the Thiele modulus is suggested which makes the asymptotic behavior of the effectiveness factor identical for all pellet shapes and all activity profiles. For an operational range intermediate between kinetic and diffusion control, however, the normalization can lead to significant errors. No such normalization exists when the surface catalytic activity is zero.     

On the prediction of crystal shape distributions in a steady-state continuous crystallizer

Zhang and Doherty [2004. Simultaneous prediction of crystal shape and size for solution crystallization. A.I.Ch.E. Journal 50, 2101-2112] have provided a one-dimensional analysis of crystallization based on the assumption that the relative face-specific growth rates of a (2-D) crystal are independent of supersaturation and hence invariant with time. Subsequent work by these authors [Zhang, Y., Sizemore, J.P., Doherty, M.F., 2006. Shape evolution of 3-dimensional faceted crystals. A.I.Ch.E. Journal 52, 1906-1915) consider shape evolution of single three-dimensional crystals with morphological changes. In this work, we present a multidimensional population balance approach accounting for dependence of the relative face-specific growth rates on supersaturation, a situation more commonly encountered. For example, Joshi and Paul [1974. Effect of supersaturation and fluid shear on habit and homogeneity of potassium dihydrogen phosphate crystals. Journal of Crystal Growth 22, 321-327] and Mullin and Whiting [1980. Succinic acid crystal-growth rates in aqueous solution. Industrial & Engineering Chemistry Fundamentals 19, 117-121] report face-specific growth rates with different dependence on the supersaturation. Thus it has been observed that there exists significantly different crystal shapes in a crystallizer [Yang, G., Kubota, N., Sha, Z., Louhi-Kultanen, M. Wang, J., 2006. Crystal shape control by manipulating supersaturation in batch cooling crystallization. Crystal Growth and Design 6, 2799-2803]. Consequently, the population of crystals at any instant will have widely varying crystal shapes and sizes depending upon the initial crystal shape and size distribution. Computations are presented for the shape distributions of the crystal population emerging from a steady-state continuous crystallizer for two cases: (1) feed without crystals including nucleation for the formation of new crystals, and (2) feed with seed crystals of known shape, with suppressed nucleation. In the range of mean residence times investigated, the calculated crystal volume distributions for the first case show geometrically dissimilar shapes without morphological variations. However, in the second case, because the feed crystals of the chosen shape were susceptible to morphological changes, the volume distributions display this feature with shape and size distributions for each of a number of different morphologies. By varying operating conditions such as the flow rate, the inlet supersaturation, and the shapes of feed crystals, the proposed model can clearly be used to manipulate the crystal shape and size distributions and their morphologies.     

汽车催化转化器数学模型的修正

催化转化器涂层和孔道之间存在着质量传递,由于涂层和孔道中物质的能量不同,在质量传递的同时必然伴随着能量传递。首先对这种伴随质量传递的能量传递进行分析,从理论上研究了这部分能量交换对计算结果的影响,得出这部分能量交换不可忽视的结论,据此对当前应用的催化转化器模型进行了改进,使计算模型在理论上更加完善,又结合试验对模型改进前后的预测结果进行了分析,验证了改进模型的有效性。     

Control of the growth of the diffusional boundary layer on a rotating axisymmetric electrode of arbitrary shape in an ostwaldian fluid

Using a suitable coordinate transformation, an analysis is first described for the prediction of the velocity distribution in a laminar boundary layer flow near a rotating axisymmetric electrode of arbitrary shape in an Ostwaldian fluid, by expressing the governing conservation equations in a series representation universal with respect to electrode contour parameters, patterned by Blasius procedure.Using the first leading term of the series, we define the profiles of the electrodes which fulfil the diffusional limiting density flux j_x = j₀$\text{x}$^p, in which j₀ is an independent coordinate coefficient, p is a numerical power-factor and $\text{x}$, is measured along the direction of the longitudinal component of the flow. The relation between the permitted values of p with the behaviour coefficient of the fluid is described. The particular case of the uniformly accessible electrode (p = 0) is discussed.     

Development of the anodized aluminum substrates for thermoelectric energy converters

Operation of the thermoelectric converters requires hot- and cold-side insulating plates with low thermal resistance. In this work, we developed anodized aluminum substrates with physical properties accommodated for thermoelectric converters, which can be a possible alternative to the expensive and brittle commercial ceramics. The XRD, SEM, and EDS analyses were employed to investigate the quality of the prepared samples. The thermal resistance of the developed substrates shows much lower values compared with the commercial ceramics indicating the beneficial effect of the anodized aluminum substrates on the heat transfer through the thermoelectric module. The temperature-dependent breakdown voltage of the Al₂O₃ anodic layer was estimated as a key parameter that defines the thermoelectric module's workability. For the measurement of the thermal breakdown voltage of dielectric layers, the temperature-controlled testing setup was developed. With the help of the Walther-Fock theory and the measured data, the analytical expression that determines the thickness of the Al₂O₃ dielectric layer as a function of the anodization voltage and temperature is proposed. Considering Seebeck voltage generated by a thermoelectric module, the desired thickness of the Al₂O₃ layer can be defined to prevent the destruction of the dielectric substrate during the thermoelectric module operation. The application of the presented results can significantly accelerate the development of mechanically strong, low-cost, and highly efficient thermoelectric energy converters.