LABORATORY CATALYTIC REACTORS

A basic requirement in the analysis of catalytic reactors is a rate expression for the reaction concerned. In the design of any equipment the equations to be used contain certain basic physical-chemical coefficients whose values must be known. In the case of physical operations, these coefficients can usually be predicted from available correlations and the design of equipment is often carried out from first principles. But there is no method available by which the kinetic rate parameters of a chemical reaction can be predicted; thus experimental determination of these parameters is unavoidable.     

The influence of solution parameters on the electrospinning intensity from foamed surface

Electrospinning is an efficient process for producing polymeric and hybrid nanofibers. There is, however, a lack of understanding concerning scalability of the process and in particular the production rate optimization. The electrospinning mass transfer intensity depends predominately on solution parameters, process parameters and the design of the equipment. These parameters influence the deposition intensity of the spinning process differently, but it is not known which factors dominate. The e‐spinning deposition intensity of polyethylene oxide, polyvinyl alcohol and their mixtures was investigated using a bubble foamed polymer solution surface to promote high mass deposition. Based on the measured properties of the solutions, a mathematical criterion was developed which made it possible to predict the electrospinning intensity of a given polymer solution. The proposed formula agrees with the experimental data and confirms that spinning intensity can be predicted from pre‐determined solution parameters. Using computer modeling, the weighting coefficients of the solution parameters have been determined, showing which parameter is the most important for the process intensity. The criterion and the same weighting coefficients were applied to the analysis of published data and it was found that they can be applied not only for electrospinning from the foamed surface but also from the free surface. A physical explanation of the criterion is proposed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42034.     

螺旋流内热虹吸沸腾装置(Ⅱ)流体流动及传热的计算

对已发表的有关螺旋通道内单相流及两相流关联式进行了讨论.在螺旋流内热虹吸装置内,除螺旋流(主流)外,还存在螺纹外缘与加热管内壁面缝隙间的旁流.此两流道内的流量分配可依据“流路分析法”的基本概念求解,而沸腾传热系数则按加权平均法求算.本文提出一个可供工程设计之用的计算方法.计算值与实验结果吻合良好.     

FLUIDISED BED DRYER SCALE-UP

Design methods for fluidised bed dryers have developed to the point where reliable scale-up is now possible for most applications. The model underlying the methods is described in terms of its constituent parts, namely a material model and an equipment model. The material model utilises drying data from laboratory tests together with scientifically based rules for predicting the effect of changes in operating conditions and the main design parameters on performance. The equipment model describes the residence time distribution for the system. This paper focuses on continuous well mixed and plug flow units.

There are a number of factors which must be considered in scale-up beyond the basic design method. In particular, the feed system, distributor, plenum and freeboard regions can introduce operational differences between the laboratory and full scale units which may adversely affect performance. Guidance is given on these practical considerations.     

FLUIDISED BED DRYER SCALE-UP

Abstract

Design methods for fluidised bed dryers have developed to the point where reliable scale-up is now possible for most applications. The model underlying the methods is described in terms of its constituent parts, namely a material model and an equipment model. The material model utilises drying data from laboratory tests together with scientifically based rules for predicting the effect of changes in operating conditions and the main design parameters on performance. The equipment model describes the residence time distribution for the system. This paper focuses on continuous well mixed and plug flow units.

There are a number of factors which must be considered in scale-up beyond the basic design method. In particular, the feed system, distributor, plenum and freeboard regions can introduce operational differences between the laboratory and full scale units which may adversely affect performance. Guidance is given on these practical considerations.     

气液两相分离器计算方法的优化

分离器是最常见的工艺设备之一。目前计算分离器大小的方法主要是根据规范标准,但标准规范具有一定的局限性。同时许多技术文献也已对分离器的设计进行了论述,大量的技术信息在许多公司的内部设计手册中也被涉及,而公开发表的文献却少见报道。此外,对于分离器尺寸设计的基本方程已众所周知,但对方程中参数的选择还有许多需要考虑和慎重的地方。因此,着力介绍了不同的分离器设计方法和分离器的设计基础理论,并提供了分离器逐步计算的新方法和计算对比实例,为分离器的设计计算提供相应的指导。     

A tool for mass transfer evaluation in packed-bed columns for chemical engineering students

This paper presents a Microsoft Excel tool to calculate liquid-gas mass transfer coefficients in packed towers to support numerical design activities in the courses of Unit Operations for Industrial Process and Sustainable Process Design for the Master’s degree in Chemical Engineering of the University of Naples Federico II (Italy).The Mass Transfer Solver Tool (MT Solver Tool) uses several available models to estimate, separately, the values of liquid and gas mass-transfer coefficients and the wet surface area for 144 random and structured packings of interest for absorption/stripping and distillation processes. In addition, a separate spreadsheet can be used in a user-defined mode, to evaluate the mass transfer coefficients with new packing types or to interpret experimental data when the geometrical and physical characteristics of the packing are known. Eventually, the tool is supplied with a data library, where packing geometry and model fitting parameters can be retrieved.The software is aimed to support students and educators in the Unit Operations for Industrial Process and Sustainable Process Design courses. In particular, this is meant to be an example on how the accuracy of design algorithms adopted in unit operation processes is affected by the use of the underpinning correlations for mass transfer rate or pressure drops. Besides, this is aimed to encourage comparison of different correlations when exact field data are not available. Besides, chemical engineers and researchers interested in packed columns design and modelling data may also benefit from the utilization of the software. The MT Solver Tool was introduced to students in a dedicated tutorial lesson after lecturers on packed column design algorithms for distillation, absorption and stripping. Most of the students of the course participated to a group training aimed to simulate the design of an absorption column supported by the MT Solver Tool providing feedback on its application.After the training, an anonymous survey was proposed to the students to monitor the approval rating of the proposed activity and the use of the MT Solver Tool software to support numerical calculations.     

谷物干燥模拟软件

介绍了CGDSP、DRYPAK、HL—E三种谷物干燥模拟软件的功能、原理和使用方法，给出了各软件的输入和输出参数。利用这些软件可以对谷物干燥机的性能进行预测以及参数选择、试验和设计，扩大了计算机在干燥技术领域中的应用，为干燥技术的发展提供了一种先进的方法和工具，具有显著的实用价值。     

Multiobjective optimization of multipurpose batch plants using superequipment class concept

We present a novel approach for solving different design problems related to single products in multipurpose batch plants: the selection of one production line out of several available, additional investment into an existing line or plant, and grass-root design of a new plant. Multiple objectives are considered in these design problems. Pareto-optimal solutions are generated by means of a Tabu Search algorithm. In the novel approach the concept of superequipment has been defined as an abstract equipment model, which is capable of performing any physico-chemical batch operation. Each superequipment is transformed into a real equipment unit, for example a reactor, during or after the optimization in order to evaluate performance parameters of a design. This novel concept uses an implicit definition of a superstructure and essentially optimizes on the transfers between different equipment units in a design.On the basis of case studies we demonstrate that the application of the superequipment concept offers a number of advantages for the investigated design problems. For example, in the evaluation of investment into single equipment pieces to be added to existing plants or production lines only the maximum number of additional equipment, each represented as a superequipment, has to be specified instead of a list consisting of a higher number of explicit units. Similar advantages arise for grass-root design problems or for the selection of a production line or plant out of several that are available for the production of a specified chemical.The comparison with optimization results obtained with a conventional Tabu Search algorithm revealed that the superequipment approach is capable of identifying the Pareto-optimal solutions in significantly reduced computation time.     

Fundamentals towards a Modular Microstructured Production Plant

For years, microtechnology is being considered as an emerging technique for chemical engineering tasks to overcome safety issues corresponding to high volumes and gaining higher selectivities and yields in reaction technology. Whereas in reaction technology a broad variety of microstructured equipment is available, in product purification/separation adequate equipment is missing. Research is focused on modular fast and flexible smaller production plants being operated continuously instead of batchwise in order to reduce engineering efforts and time‐to‐process. To cope with these demands, an appropriate definition of modules, which could be easily chosen and combined, is inevitable. In addition, these modules have to be well characterized concerning fluid dynamics and separation performance. This paper focuses on the characterization of available modules/devices. A standard method and analysis of the results concerning manufacturing accuracy and operation range is proposed. Miniplant technology is described as an efficient tool to validate process concepts proposed by process simulation studies. Necessary model parameters are determined for industrial complex mixtures in miniaturized laboratory equipment. Parameters are calculated model based to gain maximal accuracy. State of the art of miniplant technology is described and basic characteristic data are presented.     

Simulation of a jet-assisted circulation jacketed batch reactor for polymerization of methylmethacrylate

A simulation of a five-liter, agitated, nonisothermal, jet-assisted circulation, jacketed methylmethacrylate polymerization batch reactor considering all the available physical-chemical properties and related correlations for agitation and heat transfer coefficients is presented. From the calculated cumulative radical population, the phenomena of early runaway, thermal ignition and gel effect ignition are identified. Variations of medium viscosity over the course of the polymerization reaction affect the performance of the agitator and the overall heat transfer coefficient. The simulation results indicate that much higher heat duties can be removed by this special equipment design than in the case of a conventional vessel design.     

The effect of mineral composition on the interaction of strontium ions with geological formations

The surface reaction of strontium ions was studied on rock samples with a radioactive tracer method. The experimental distribution coefficient was calculated from the equilibrium adsorption yield. The distribution coefficient of montmorillonite, rectorite, illite, quartz and cristobalite was determined from the mineral composition and the distribution coefficient of samples with a linear model. On the basis of our linear model and the distribution coefficients of the mineral components, the equilibrium sorbed quantities of strontium ions (or other cations) on any rocks can be predicted when we determine the mineral composition (and the distribution coefficients of the minerals for the given cation). It is very advantageous because of the great variety of geological formations, a lot of experimental work can be neglected. The adsorption parameters make possible the prediction of the migration properties, too. This model can also be used for the design of a geological radioactive waste repository.     

Prediction of osmotic pressures of polymer solutions

A theory which has been developed to account for the effects of concentration on the equivalent hydrodynamic volumes of dissolved polymers has been combined with a statistical mechanical relation for the virial coefficients of dilute suspensions of rigid spheres. With a scaling factor for solvent goodness, osmotic pressures of polymer solutions can be predicted with good accuracy. The input parameters needed are the number-average molecular weight of the polymer sample and its intrinsic viscosity in the solvent of interest, as well as its intrinsic viscosity under theta conditions. The intrinsic viscosities can be estimated with sufficient accuracy from tabulated Mark–Houwink coefficients. The model developed contains no adjustable parameters. Comparisons of predicted and reported experimental osmotic pressures are presented, and a method for prediction of second virial coefficients is described.     

Modeling thermodynamic properties of aqueous single‐solute and multi‐solute sugar solutions with PC‐SAFT

The Perturbed‐Chain Statistical Association Fluid Theory is applied to simultaneously describe various thermodynamic properties (solution density, osmotic coefficient, solubility) of aqueous solutions containing a monosaccharide or a disaccharide. The 13 sugars considered within this work are: glucose, fructose, fucose, xylose, maltose, mannitol, mannose, sorbitol, xylitol, galactose, lactose, trehalose, and sucrose. Four adjustable parameters (three pure‐sugar parameters and a k_ij between sugar and water that was allowed to depend linearly on temperature) were obtained from solution densities and osmotic coefficients of binary sugar/water solutions at 298.15 K available in literature. Using these parameters, the sugar solubility in water and in ethanol could be predicted satisfactorily. Further, osmotic coefficients and solubility in aqueous solutions containing two solutes (sugar/sugar, sugar/salt) were predicted (no additional k_ij parameters between the two solutes) reasonably. The model was also applied to predict the solubility of a sugar in a solvent mixture (e.g., water/ethanol) without additional fitting parameters. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4794–4805, 2013     

Performance of a venturi jet scrubber for H2S removal by iron-complex solution

Venturi jet scrubbers are widely used in chemical industries as an efficient gas-liquid contacting equipment. They are simple in design, have no moving parts, operate with circulating liquid and are reliable in service. Moreover, due to high relative velocity of liquid and gas, considerable overall mass transfer can be produced. In spite of their wide application, readily usable design data are not available in literature, particularly for units producing a gas flow by their own pumping action. The purpose of this paper is to introduce the equipment and its application for H₂S removal. The effects of various parameters such as gas and liquid flow rates as well as pressure on hydrodynamics and mass transfer performance of the equipment are investigated. Results of experiments have been shown graphically.     

Integration of modern computational chemistry and ASPEN PLUS for chemical process design

Thermodynamic properties and fluid phase equilibria are crucial for the design and development of a chemical process. However, such data may not always be available, particularly for fine or specialty chemicals. In this work, we evaluate the reliability of using modern computational chemistry combined with recently developed predictive thermodynamic models to provide all the thermodynamic properties required in process design with ASPEN PLUS. Specifically, the G3 method is used for the ideal gas heat capacities and properties of formation, and the PR+COSMOSAC equation of state and COSMO-SAC activity coefficient model are utilized for the properties and phase behaviors of pure and mixture fluids. These methods are chosen because they do not require any species-dependent parameters and can, in principle, be applied to any chemical species. For a set of 972 chemicals, it is found that most properties can be predicted with a satisfactory accuracy (less than 10%: critical temperature [5%], critical pressure [10%], critical volume [5%], constant pressure ideal gas heat capacity [5%], and heat of vaporization [10%], except for the acentric factor [33%] and vapor pressure [73%]). Furthermore, the predicted results show little bias suggesting that these theoretically based methods are reliable for new chemicals for which experimental data are not yet available. Our analyses show that better accuracy in the prediction of vapor pressure and formation enthalpy and free energy is necessary for the design of chemical processes without relying on any experimental input. Nonetheless, these methods often provide reliable relative property values (e.g., relative value of normal boiling temperature can be predicted with 94% accuracy), making it possible to screen for new chemicals for improving existing processes.     

Isothermal reaction calorimeters—I. A literature review

Most chemical and physical processes are accompanied by heat effects. These heat effects may contain significant information concerning the mechanism of the process, and a safe scale up of the process often requires a quantitative knowledge of the heat generated or consumed. In the present review one particular laboratory equipment for measurement of heat effects—the isothermal reaction calorimeter—will be described. Part I is a literature study of the available calorimeter equipment. Isothermal reaction calorimeters are described and classified according to the measurement principle of the particular design. Part II describes different techniques for numerical treatment of calorimeter data. It is argued that modern filtering methods and careful mathematical modeling can be used to obtain a significant improvement in the determination of physical and chemical parameters from calorimeter experiments. Finally, as an example a new data treatment system for a commercial bench scale isothermal calorimeter will be discussed.     

Vortex nozzles for limitation of discharge rates

The vortex nozzle, employing the radial pressure differential across a vortex can be effective in limiting the discharge of fluid or slurries from pressurized systems without using small throttling orifices which could plug readily. This paper deals with an investigation of vortex discharge devices which use this principle: It features measurements of velocities using a photographic trace technique. The measured radial distribution of mean tangential velocity departed from a free vortex pattern due to friction losses at the walls of the equipment. Empirical equations were developed for the tangential velocity and the flow, the coefficients being related to parameters of the design.