Production of zinc ferrite in a mechano-chemical reaction by grinding in a ball mill

Zinc ferrite was obtained by prolonged dry grinding of stoichiometric powder mixtures of ZnO + -Fe₂O₃ or ZnCO₃ + -Fe₂O₃. The kinetics of transformation was studied by X-ray diffraction, Mössbauer spectroscopy and DTA. Crystallite size reduction followed the process, and defect structures resulted. The carbonate decomposed as a necessary step in the process. In the mixture of NiO + -Fe₂O₃, nickel ferrite was not obtainable, although considerable grain size reduction was observed. This was attributed to the inverse spinel configuration of the nickel ferrite, differing from the normal spinel configuration of the zinc ferrite. In the -Fe₂O₃ and the zinc ferrite, iron ions occupy octahedral sites, while in ZnO and the ferrite, zinc ions occupy tetrahedral sites, and metal ion—oxygen distance is almost identical. These facilitate the transformation. In the nickel ferrite, iron ions occupy both sites, which calls for high strains of -Fe₂O₃ before it can undergo transformation. Further implications of the processes are discussed.     

Studies on modeling and control of spouted bed reactors—II: Control

Control and operability characteristics of an adiabatic spouted bed reactor with a first order reaction are investigated. The reactor transient response to changing operating conditions is analyzed and the generic control problems are formulated. Reduced-order state space models suitable for process control studies are constructed by utilizing the methods of orthogonal collocation and singular perturbation.Based on modern control and estimation techniques a hierarchy of different control systems is systematically generated. The assessment of alternative d     

Azo disperse dyes with polyfluoroalkyl groups attached to the nitrogen atom of the coupling component

A number of new azo disperse dyes with polyfluoroalkyl groups attached to the nitrogen atom of the coupling component have been prepared. The influence of polyfluoroalkyl groups on the colour and properties of azo dyes has been studied. The replacement of hydrogen atoms of the methyl group of the coupling component by polyfluoroalkyl radicals causes a hypsochromic shift of absorption maximum in a neutral solution and deepening of the dye colour in an acid solution. All tested dyes showed a high lightfastness on acetate and polyamide fibres.     

1，3－取代方酸衍生物的光谱研究及二聚体、簇集体的形成

本文合成了１，３－取代方酸衍生物：１，３－双［４－二甲胺苯基］－２，４二羟基环丁二烯氢氧双内盐（ＤＭＣＳ），１，３－双［４－双十六烷胺苯基］－２，４二羟基环丁二烯氢氧双内盐（ＤＨＣＳ）。研究了ＤＭＣＳ和ＤＨＣＳ在不同溶剂中的光物理行为，估算了ＤＭＣＳ、ＤＨＣＳ的基态与激发态之间偶极矩差值。在ＣＴＡＢ胶束中，除ＤＭＣＳ单体分子外，ＤＭＣＳ形成了二聚体。在二氧六环－水体系中，研究了ＤＨＣＳ的簇集行为，并测定了ＤＨＣＳ的临界簇集组成（Ｃ＿ψ）及临界簇集浓度（Ｃ＿Ａ）     

竹红菌甲素衍生物13－SO_3Na－DDHA电化学及光诱导还原的研究

本工作研究了化合物１３－ＳＯ＿３Ｎａ－ＤＤＨＡ在不同ｐＨ的缓冲溶液中的电化学氧化还原行为．实验证明：化合物中羰基的还原电位与ｐＨ之间存在线性关系，其直线的斜率为６０ｍＶ／ｐＨ．并证明了此过程为一步两电子、两质子还原过程：Ｑ＋２Ｈ￣＋＋２ｅ＝ＱＨ＿２．ＤＭＦ作为非质子溶剂，具有很好的稳定自由基的作用．向缓冲溶液中加入ＤＭＦ后，化合物１３－ＳＯ＿３Ｎａ－ＤＤＨＡ为两步单电子还原过程，相应溶液中的光诱导电子转移吸收光谱证实了以上电化学的结果．     

Experimental observation of temperature gradients occurring in a single zeolite pellet

An experimental study has been made of temperature profiles incident within a zeolite adsorbent particle in the course of adsorption of n-heptan. Using thermocouple wires 0.1 mm in diameter it has been possible to measure simultaneously the temperatures of the surface and in the centre. It was observed that temperature differences between center of the pellet and ambient stagnant gas may be more than 20°C. The results of this work indicate that the overheating of an adsorbent particle is a very rapid process which is followed by a slow cooling of the hot particle. Experimental data are compared with predictions calculated from the theoretical model.     

Flow distribution and pressure drop in plate heat exchangers—II Z-type arrangement

To investigate the flow distribution and the pressure drop in the Z-type arrangement plate heat exchangers, a theoretical analysis has been made including mass and momentum balances for a flow element in both the intake and exhaust conduits. Calculations based on one-dimensional flow equations have been carried out.It is found that the flow distribution and the pressure drop can be determined by a general characteristic parameter (m). Nearly uniform flow distribution may be obtained when m is equal to zero. In the case when m² is positive, the channel flow rates will increase in the direction of the intake stream. If m² is negative the channel flow rates will also increase in the intake stream direction. The analysis also shows that the total pressure drop in plate heat exchangers is practically the same for both U - and Z-type arrangements. The results are applicable to a wide variety of combinations of heat exchanger dimensions, channel goemetries and fluid velocity. They are summarized by charts that permit a designer quickly to estimate the flow patterns.     

Vapour liquid equilibrium with association in both phases: A model with the concentration-dependent liquid phase association constant applied to acetic acid—benzene, -toluene, -p- and -o-xylene

A model employing the correction factors of Marek and Standart, but using a concentration-dependent liquid phase association factor of Jenkins—Robinson, has been used to model vapour—liquid equilibrium data for mixtures of acetic acid with benzene, toluene, o-xylene and p-xylene. With the aim to use systems of acetic acid—benzene and acetic acid—toluene as the test mixtures for distillation columns, the examination of the systems of acetic acid—aromatic hydrocarbons was undertaken. The model promises to be useful in modelling isobaric and isothermal data of acetic acid—benzine, acetic acid—toluene, acetic acid-p-xylene and acetic acid-o-xylene systems. Deviation plots show that the isothermal and isobaric data are represented well.     

A modification of broyden's method for the solution of sparse systems—with application to distillation problems described by nonideal thermodynamic functions

An algorithm that permits Broyden's method to be used for the solution of large systems of algebraic equations with sparse Jacobians is presented. The new procedure is compared to Schubert's modification of Broyden's method and to the Newton-Raphson method by solving an extractive distillation problem. It is demonstrated that the new procedure is competitive with Schubert's method when it is necessary to evaluate Jacobian matrices numerically.     

Exploiting border structure in solving large sparse linear systems in bordered triangular form

An elimination strategy for solving sparse linear systems in bordered triangular form is presented. This strategy is designed to exploit certain common structural properties of the borders of such a system. It may also be interpreted as a recursive application of block elimination. The technique is numerically efficient and provides significant reductions in fill-in compared to routine Gaussian elimination. It is applicable in the iterative solution of the large systems of nonlinear equations that arise in the equation-oriented approach to process simulation and design calculations, as well as in other problems of interest to the chemical engineer.