An improved falling-film reactor for viscous liquids

This paper presents the design of a sulfonation reactor that is intended for enhanced performance when the viscosity of the liquid phase increases, thus reducing gas-liquid transfer rates. The proposed design allows adequate transfer rates to be maintained by progressively increasing the shear stress exerted by the gas over the liquid film. The effectiveness of the design has been tested in runs in which dodecylbenzene and lauryl alcohol 1.80E are sulfonated/sulfated.     

Mixing for reaction injection molding. I. Impingement mixing of liquids

The performance of confined impinging jet mixers, commonly used in reaction injection molding, was investigated. A theory is presented which assumes that large scale mixing is always adequate, provided the mixer operates in turbulent flow, and argues that the scale of segregation of the final mixture should depend on the size of the smallest eddies of the turbulent motion. The theory predicts that a length scale describing the quality of the mixture will decrease like the nozzle Reynolds number to the ?3/4 power. Flow visualization experiments were used to find the point of transition to turbulent mixing flow. This transition occurs at a nozzle Reynolds number of 140 for directly opposed nozzles and at higher Reynolds numbers for nozzles angled downstream. Other geometric factors have little influence on the transition point. Quantitative mixing experiments using model fluids support the theory. Momentum ratio is shown to have no effect on mixing quality.     

New characterization techniques for coal-derived liquids

Development of understanding of the chemistry of coal liquefaction is often limited by the tools available to study compositional change. This paper discusses several new and useful techniques for characterization of coal-derived liquids. A single method of analysis is shown to be much less informative than the combined results from several methods. In particular, combinations of liquid chromatography, gas chromatography, and field ionization mass spectroscopy (FIMS) are shown to be particularly useful. Liquid chromatography offers a convenient method to isolate chemically distinct fractions of both distillates and non-dstillates which on subsequent further characterization can yield insight into understanding the chemistry involved in coal liquefaction. Through sophisticated data manipulation mechanistic information can be gained via FIMS which would be nearly impossible to achieve using other characterization tools.     

Experiments in extensive mixing in laminar flow. I. Simple illustrations

Simple quantitative mixing experiments in well-defined deformations clearly demonstrate the validity of previously derived equations relating deformation and mixing. A simple mixture of black and white polyethylene is studied by direct measure of striation thickness. The well-known linear relationship in simple shear is demonstrated. By using a simple method for uniform reorientation, the second power relationship in shear once interrupted, the third power relationship in shear twice interrupted and the fourth power relationship in shear interrupted three times are demonstrated. In uniaxial elongational mixing of a silicone fluid, exponential dependence of mixing on strain is demonstrated.     

Experimental investigation of transition to laminar mixing of a homogeneous viscous liquid in a tilted-rotating tank

A tilted and partially filled rotating tank is investigated experimentally at O(1) Reynolds and small (?1) capillary numbers, to study the mixing of a viscous homogeneous fluid. Of particular interest is the transition from a previously studied low Reynolds number flow regime [Ward, T., Metchik, A., 2007. Viscous fluid mixing in a titled tank by periodic shear. Chemical Engineering Science 62, 6274-6284], that exhibited two large vortices, to the laminar flow regime which results in additional vortex generation. In the laminar Reynolds number limit O(1) the two primary vortices generated by the liquid rotation axis can interact with the bottom wall, generating two secondary counter-rotating vortices, via a cascade that is qualitatively similar to the well known Moffatt [1964. Viscous and resistive eddies near a sharp corner. Journal of Fluid Mechanics 18, 1-18] vortices in Stokes flow. While the secondary vortices aid in transporting material from the walls to the bulk, they also intensify in magnitude with increasing rotation rate leading to finite sized unmixed regions via the appearance of KAM-like surfaces [Alvarez-Hernández, M.M., Shinbrot, T., Zalc, J., Muzzio, F.J., 2002. Practical chaotic mixing. Chemical Engineering Science 57, 3749-3753]. This suggests that there may be an optimal tilt angle, for a given speed, with which to achieve the maximum mixed cross sectional area within a minimum amount of elapsed time. Experiments are performed using a 90% glycerol, 10% water mixture at two volume portions with angles ranging between 25^° and 65^° measured from the horizontal. Laser fluorescence is used to illuminate the vortices via experimental Poincaré mapping [Fountain, G.O., Khakhar, D.V., Ottino, J.M., 1998. Visualization of three dimensional chaos. Science 281, 683-686], and the resulting images are analyzed to determine the mixed cross sectional area versus elapsed time.     

Clarification of liquids using filter aids Part I. Mechanisms of filtration

Filter aids were characterized by an effective particle diameter and a pore diameter in the filter aid cake, calculated from the specific cake resistance using the Kozeny equation. The results agreed well with those from mercury porosimetry. The transition from surface filtration to depth filtration by filter-aid cakes was studied with uniform polystyrene particles as a model impurity. The critical ratio between pore diameter and impurity diameter was between 2 and 3. At conditions of non-surface filtration, an important concentration of impurity exists in the liquid flowing through the cake causing a danger of blocking. When pre-coat and body feed were used with polystyrene particles as an impurity, the blocking appeared to occur rather easily on top of the original pre-coat and on the filter medium. The type of pre-coat and the way in which it was formed were very important. In beer filtration, which is mainly a surface filtration, a small concentration of passing impurity was able to block the pre-coat layer, when the filter aid of the body feed was coarser than that of the pre-coat.     

Electrochemical repair techniques in carbonated concrete. Part I: electrochemical realkalisation

Corrosion induced by concrete carbonation can be controlled through the application of electrochemical techniques such as cathodic protection (CP) or electrochemical realkalisation (ER). These methods are generally considered effective in the repair of structures; however, few data are available on the effects of different parameters such as the concrete composition or the exposure conditions. For the temporary technique of ER, moreover, scarce information exists on the durability of the treatment. An experimental research was carried out, aimed at investigating some aspects connected with the application of these techniques in reinforced carbonated concrete. Six different types of concrete mixes were considered. The tests were performed both in a wet and a dry environment. The effect of the pre-corrosion of the reinforcement in concrete was also considered. This article presents results obtained with the technique of ER and discusses the role of the different factors considered. The technique of CP will be discussed in Part II.     

Production of commercial dyes via impingement-sheet mixing: Part I. Testing of a device suitable for industrial application

Impingement-sheet mixing is a proven technique for the rapid mixing of liquids on the laboratory scale. In this paper a practical mixer design for use on the industrial scale is presented. The industrial impingement-sheet mixer was tested at flow rate ratios typical of commercial applications and, compared with earlier laboratory results, only a slight loss in mixing speed was noted. At flow rates of the order of liters/minute and pressure drops up to 1.5 bar, the micromixing times of the industrial impingement-sheet mixer are of the order of tens of milliseconds for reactant stoichiometric ratios near 1.00. If one of the reactants is present in at least a 10% excess, then the micromixing time of the limiting reagent is reduced to several milliseconds.     

A new approach to mixing techniques for enhanced performance in automated sample preparation

In the automation of sample dilution or derivatization, the performance of the mixing technique employed when adding solvents or reagents to samples is critical. This paper presents a newly developed mixing method, based on conventional aspiration and dispensing of liquid techniques, but which considerably improves the precision of mixing. The paper discusses the results of a comparison of the technique with other methods and describes the application of the technique to several different types of sample solutions, including a highly concentrated glucose solution. The mixing technique was performed on a Gilson XL Sampling Injector, with a 1/25 dilution of a paraben solution in 2 ml vials to give relative standard deviations of 0.2 to 0.3% (N =10).     

Simulation of aerosol dynamics and transport in chemically reacting particulate matter laden flows. Part I: Algorithm development and validation

To accurately predict aerosol dynamics in various systems, it is imperative to combine the governing equations for transport of momentum, mass and energy as well as reaction kinetics with an accurate procedure for solving the general dynamic equation (GDE). A generalized approach for solution of the GDE based on the discrete-sectional approach in presence of convective and molecular transport is presented. As computational efficiency is an important factor in realistic implementation of such a model, in Part-I of this two-part paper series an adaptive semi-implicit algorithm based on the concept of operating splitting is presented. It is shown that this algorithm is the method of choice for solving the GDE in presence or absence of convective transport based on a discrete-sectional approach.     

Longitudinal mixing of granular material flowing through a rotating cylinder— Part I. Descriptive and theoretical

The types of motion, relative displacements and mixing of solid particles moving radially and longitudinally in a partly filled rotating cylinder under various operating conditions are treated. Ball mills, rotary driers, kilns, cereal steamers and drum mixers are discussed. A short survey of the theory of longitudinal mixing is given and the applicability of the general diffusion model to the continuous flow of granular solids through a rotating cylinder is indicated.     

Analysis and evaluation of permeability techniques for characterizing fine particles Part I. Diffusion and flow through porous media

The specific surface area and particle size can be deduced with speed and simplicity from appropriate measurements and calculations of fluid flow and diffusion in porous media. The interdependence of these two processes is developed in a series of two articles.In Part I, models are presented for molecular and Knudsen diffusion during flow through aggregates of solid particles at both atmospheric and low pressure permeametric conditions. For a randomly packed bed of granular particles, a cell model is developed that takes into account the tortuosity and variations in the cross-sectional area. A new analytical expression for the Kozeny constant is derived in terms of the bed porosity and particle shape. The effect of porosity on surface area measurements using permeability methods is explained.     

New mixing rules for the BWR parameters to predict mixture properties

New mixing rules which are general and easy to use have been developed to predict the properties of mixtures from the BWR equation. The rules contain a binary interaction parameter, readily obtainable from the experimental values of the second virial cross-coefficients. The mixing rules were used to predict the densities of binary mixtures of carbon dioxide with methane, ethane and propane at elevated pressures. For any of the three mixtures, the standard error of the predictions was approximately equal to or less than the sum of the standard errors of fit for the pure components. The BWR parameters for the pure components, required in the above predictions, were determined by minimizing the sum of relative error squares in specific volume.     

3-D structure-property relationships in rolltruded polymers. Part I: Mechanical property enhancement in three directions

The effect of rolltrusion, a solid state deformation process, on the three dimensional mechanical properties of several polymers has been measured. Polymers studied included isotactic polypropylene (iPP), polyvinylidene fluoride (PVDF), and propylene/ethylene block copolymers. It was found that mechanical strength is enhanced triaxially for all these specimens upon rolltrusion. Material stiffness also exhibits 3-D improvement, depending on the polymer type and processing conditions. These new results are discussed in regard to some structural models in the literature.     

Structure and Reactivity of Spruce Mechanical Pulp Lignins Part I. Bleaching and Photoyellowing of in situ Lignins

This paper reports the structural investigation of a series of in situ spruce lignins in wood, thermomechanical pulp (TMP) and the corresponding bleached (BTMP) and photoyellowed (YBTMP) samples. This was achieved by using an original two-step degradative technique, thioacidolysis followed by Raney nickel desulfuration. The determination of thioacidolysis monomeric and dimeric products allowed an estimate of various lignin building units and interunit bonds, respectively. It was observed that the thermomechanical and bleaching treatments did not affect spruce lignin structure to an appreciable extent. On the contrary, the photoyellowing treatment caused marked structural changes in lignin, particularly when run in severe conditions. These changes were essentially a decrease in the amount of β-O-4 and β-1 interunit bonds and a relative increase in catechol units and in vanillin end-groups.     

New approach to the application of multilayer superthin coatings. Effects of mixing

It is shown within the framework of molecular-dynamic modeling that the interaction of a nonlinear pulse with a free surface can result in the separation of an atomic plane. According to the results obtained upon colliding with the target, the separated fragments can form a multilayer coating. This has formed the basis of the proposed approach to the level-by-level application of thin coatings. It is shown that the change in the number of pulses and in the time for which they reach the surface of a “source” can significantly change the structure and composition of the coating at the target. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4, pp. 137–139, July–August, 2000.     

Spontaneous imbibition of liquids in glass‐fiber wicks. Part I: Usefulness of a sharp‐front approach

Spontaneous imbibition of a liquid into glass‐fiber wicks is modeled using the single‐phase Darcy's law after assuming a sharp flow‐front marked by full saturation behind the front occurring in a transversely isotropic porous medium. An analytical expression for the height of the wicking flow‐front as a function of time is tested through comprehensive experiments involving using eight different wicks and one oil as the wicking liquid. A good fit with experimental data is obtained without using any fitting parameter. The contact‐angle is observed to be important for the success of the model—lower contact angle cases marked by higher capillary pressures were predicted the best. The proposed model provides a nice upper bound for all the wicks, thereby establishing its potential as a good tool to predict liquid absorption in glass‐fiber wicks. However, the sharp‐front model is unable to explain region of partial saturation, thereby necessitating the development of part II of this article series (Zarandi and Pillai, Spontaneous Imbibition of Liquid in Glass fiber wicks. Part II: Validation of a Diffuse‐Front Model. AIChE J, 64: 306–315, 2018) using Richard's equation. © 2017 American Institute of Chemical Engineers AIChE J, 63: 294–305, 2018