Length to diameter ratio of extrudates in catalyst technology I. Modeling catalyst breakage by impulsive forces

Natural or forced catalyst extrudate breakage is an important phenomenon during catalyst manufacture. Here, a two‐parameter model for predicting the reduction in the length to diameter ratio of catalyst extrudates due to breakage by impulsive forces as experienced in a laboratory drop test is developed. Part II will show how both parameters can be correlated with the strength of the extrudates and the severity of the drop test. For breakage by impulsive forces, the model reveals that extrudates are reduced in length to diameter ratio according to a pseudosecond‐order break law. Also, a tie‐in exists with the well‐known Golden Ratio that is famous for its inherent esthetic value. Applying the model to cases of “severity sequencing” and “severity conditioning” reveals the nonlinear behavior of the length to diameter ratio and yields results that are often nonintuitive and hard to get without this engineering analysis. © 2015 American Institute of Chemical Engineers AIChE J, 62: 639–647, 2016     

Preferentially oriented BaTiO3 thin films deposited on silicon with thin intermediate buffer layers

Barium titanate (BaTiO₃) thin films are prepared by conventional 2-methoxy ethanol-based chemical solution deposition. We report highly c-axis-oriented BaTiO₃ thin films grown on silicon substrates, coated with a lanthanum oxynitrate buffer layer of 8.9 nm. The influence of the intermediate buffer layer on the crystallization of BaTiO₃ film is investigated. The annealing temperature and buffer layer sintering conditions are optimized to obtain good crystal growth. X-ray diffraction measurements show the growth of highly oriented BaTiO₃ thin films having a single perovskite phase with tetragonal geometry. The scanning electron microscopy and atomic force microscopy studies indicate the presence of smooth, crack-free, uniform layers, with densely packed crystal grains on the silicon surface. A BaTiO₃ film of 150-nm thickness, deposited on a buffer layer of 7.2 nm, shows a dielectric constant of 270, remnant polarization (2P_r) of 5 μC/cm², and coercive field (E_c) of 60 kV/cm.     

Catalyst deactivation by site coverage and pore blockage: Finite rate of growth of the carbonaceous deposit

The deactivation of a catalyst by coke deposition is described in terms of two mechanisms: site coverage and pore blockage. The blockage is caused by coke growing from a precursor covering a site. Previous work by the authors considered the rate of growth of the coke to be infinite, but the present paper generalizes the theory to allow for finite rates. The relation between the deactivation function and the coke content is derived for single ended pores, for pores open at both ends and for networks of pores.     

Pyrolysis of waste using a hybrid argon–water stabilized torch

An experimental plasmachemical reactor equipped with the novel IPP-ASCR hybrid gas–water stabilized DC torch (160 kW) has recently been started at IPP Prague for the innovative and environmentally friendly plasma treatment of waste streams with a view to their sustainable energetic and chemical valorization and to a reduction of the emission of greenhouse gases. Since the process energy is provided by direct heat transfer from plasma, gases of widely varying chemical composition may be used. The use of electrical energy also reduces the gas flows and requirements for exhaust-gas treatment, and offers control over the chemistry. Pyrolysis of biomass was experimentally studied using wood chips as a model substance. Syngas with a high content of hydrogen and CO was produced. The influence of adding CO₂ for increase of oxygen content in the reactor was investigated.     

Digital titration: Automated image acquisition and analysis of load and growth of Chlamydophila psittaci

Traditionally, the amount of infective chlamydiae in a given sample is determined by inoculating dilution series into cell cultures and physically counting chlamydial inclusions. This approach is time consuming, tedious, and error prone, mainly when dealing with high titers. Therefore, this paper describes a largely automated technique that was developed to standardize the determination of chlamydial load in vitro. Cells are fixed at 36 h post-inoculation and bacteria visualized using standard immunological detection methods. Consequently, for 81 microscopic fields, an image is recorded at the interpolated focal plane. These images are then automatically processed using an ImageJ plugin and the obtained results are imported into Excel to determine the number of inclusion forming units per mL in the sample. The main advantage of this technique is that no or minimal sample dilution is required, thus minimizing dilution errors. In addition, this technique was employed during the early, middle and late growth stages of the chlamydial developmental cycle and results correlated well (P < 0.01) with 16S rRNA values from previous experiments, thereby proving its suitability to follow chlamydial growth in vitro. The method described is highly suitable for high throughput titration of cell culture inoculated samples and assessment of possible antichlamydial effects of novel compounds throughout the chlamydial growth cycle. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc.     

Realization of a Four-Electrode Liquid Crystal Device With Full In-Plane Director Rotation

A liquid crystal device with micrometer-scale hexagonal electrodes has been fabricated and characterized. By using weak anchoring at the liquid crystal interfaces, the orientation of the director is completely governed by the applied electric fields. The appropriate voltage waveforms applied to electrodes allow the director in the liquid crystal layer to be rotated in the plane parallel to the substrates over large angles, exceeding 180 deg. This paper is a technological and experimental verification of an earlier proposed device concept     

Length to diameter ratio of extrudates in catalyst technology II. Bending strength versus impulsive forces

This article describes the reduction of the length to diameter ratio of extrudates, by breakage on collision with a surface. The approach links the rupture force of the extrudate by bending to the impulsive force the extrudate experiences due to collision. The bending or flexural strength of the extrudate is described by the Euler‐Bernoulli modulus of rupture. The impulsive force the extrudate experiences is described by Newton's second law. We apply the force balance at the asymptotic length to diameter ratio which is reached after many repeated impacts. This balance yields a dimensionless group as the ratio of the rupture force by bending to the impulsive force by collision. The analysis shows that the asymptotic length to diameter ratio is directly proportional to the square root of this group. This dimensionless group also allows one to define a severity of the collision via the impact velocity and the time of contact of the collision. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2658–2669, 2016     

An easy and versatile embedding method for transverse sections

In several research areas, transverse sections are indispensable for studying structural aspects of specimens. However, the oriented embedding of small cylindrical samples can become problematic, especially when transverse sections at right angles to the main axis of the object are desired. Here, we describe an easy and low‐cost technique for oriented embedding of small (? < 500 µm) as well as of larger specimens (? > 500 µm). The usefulness of the technique is demonstrated for roots and stamens of Arabidopsis thaliana and for adventitious roots of Asplenium demerkense, as examples of small and larger cylindrical samples, respectively. Furthermore, several types of resin (glycol methacrylate, epoxy and acrylic resins) were successfully tested, showing the applicability of the technique for light and electron microscopy and for immunolocalizations. In conclusion, the principle of the technique can be extended to several resins and a wide variety of specimen types, such as stems, leaves and textile fibres. The originality of the technique lies in its simplicity combined with its high efficiency to produce well‐oriented transverse sections.     

Measurement of residence time distribution in a rotary calciner

Rotary calcination is widely used in catalyst manufacturing and many other industrial processes. In this article, the influence of operational variables and material properties on the mean residence time (MRT), hold up, and axial dispersion was investigated in a pilot plant rotary calciner. Residence time distributions (RTD) of spherical, cylindrical, and quadrilobe catalyst particles were measured and contrasted. The Saeman's model was successfully applied to predict the experimental bed depth and the MRT as particles flowed through the calciner. It was observed that increasing the feed rate did not significantly affect the MRT. Results for the different particles indicated that cylinders and quadrulobes exhibited less axial dispersion than spheres due to the decreased flowability. A reliable method was developed to provide a reasonable RTD prediction in rotary calcination systems. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4068–4076, 2013     

变频电机中电磁线劣化的研究

本文的主要目的是提供有关在变频器工作状态下的电机内绝缘过早发生破坏起因的信息和数据。讨论了能预计电机绝缘寿命的标准试验方法和其他替代方法。这些数据包括了不同绝缘构造、类型和不同变频驱动装置／电机／电缆组合的寿命曲线。也介绍和讨论了有关电压、温度、绝缘构造和类型的联合效应的数据。