Oxygen transport rate on Rhodococcus erythropolis cultures: Effect on growth and BDS capability

The influence of oxygen transport rate on Rhodococcus erythropolis cultures has been studied in a stirred tank bioreactor under different transport and uptake conditions. Oxygen uptake rate has been measured by applying a modified dynamic method and a kinetic model is proposed, obtaining the kinetic parameter values: specific maintenance and yield coefficients. The volumetric mass transfer coefficients under inert conditions, k_La, and during the bioprocess, K_La, have been determined. The values obtained are different and a biological enhancement factor E, has been considered. These parameters have been predicted by the theoretical model and good agreement with experimental data under the conditions studied has been found. The oxygen limitation has been expressed by a modified dimensionless Damköhler number, Da, the relationship between transport and biological reaction rates. This number decreases with increasing stirrer speed; that is, when mass transport resistance decreases. The efficiency of oxygen utilization can be determined by a film effectiveness factor, η. The effectiveness factor was found to be a strong function of Damköhler number and decrease with increasing Da. Furthermore, oxygen concentration into culture depends on the mass transfer and consumption rates. The theoretical model proposed is able to reasonably predict the evolution of dissolved oxygen concentration with time of cultivation.     

德国艾柯夫SL-500采煤机变频器故障及分析

晋城煤业集团引进德国艾柯夫SL-500采煤机,在使用过程中,短时间内连续出现多台变频器烧坏现象,这在艾柯夫采煤机使用过程中是从未有过的事,也给本公司的原煤生产造成了很大影响。为了杜绝此类事情的再次发生,特对本次的故障排除方法进行了认真的分析总结,为今后应用与修理采煤机提供了意见。     

Numerical simulation of dispersed gas-liquid flows

This paper reviews the available information on numerical simulation of dispersed gas-liquid flows. Emphasis is on informing the reader about various aspects of constructing simulation models rather than giving an exhaustive literature review. The information is organised in a way so as to provide answers to the following questions: how to formulate model equations? how to select suitable algorithms and numerical techniques to solve these model equations? how to translate these into workable computer codes? how to use such codes for simulating flows in industrial equipment? Though greater emphasis is given to dispersed gas-liquid flows, the methodology can be applied to any multi-phase problem. Special features of multi-phase flow simulation over single-phase simulation are highlighted. A case of gas-liquid flow in a bubble column is presented as an illustration for the general methodology. The simulated mean flow field agrees reasonably with the experimental data. Properly validatedcfd codes thus can serve as a useful tool for design engineers of multi-phase systems. Some of the common pitfalls in using simulation codes for design are also discussed. This review is expected to give an overall idea about the present state-of-art of two-phase simulation in industrial equipment.     

银基电接触材料改性及制备工艺

概述了银基电接触材料的发展,介绍了Ag-Ni、Ag-C、Ag-WC和Ag-MO4个主要系列的银基电接触材料的特点及其改性方法,比较了不同银基电接触材料改性前后的优缺点。同时,叙述了粉末冶金法、合金内氧化法及预氧化合粉末法等银基电接触材料的制备工艺。最后指出,提高银基电接触材料的性能、发展新型的节银触头材料和复合触头材料是今后银基电接触材料的发展方向。     

智能交流接触器与现场总线

本文在分析智能接触器发展前景的基础上，结合现场总线说明数据通讯能力对于接触器监控的重要性。利用计算机强大的图形处理和数据计算能力。将工业现场一定数量的接触器应用现场总线组成控制局域网，通过监控计算机实施本地或远程监控和管理。     

扩展接触器零部件通用性的研究

本文介绍了一种只用十几个分立元件的电子模块，与大型接触器配合使用，可使接触器节省铜线材料60％～70％，大大减少电磁系统的体积。预置电子模块的参数，可实现交流接触器在起动过程、吸持过程的最佳电流控制，为扩展接触器零部件通用性研制出节能、节材、无噪声等性能优良的小型而容易实施的交流接触器产品提供了依据。     

Current problems in the modelling of chemical reactors

Modelling of chemical reactors is reviewed with an emphasis on process development and scale-up. A distinction is made between modelling of chemical kinetics, of rate processes in volume elements and of whole reactors. Examples are mainly taken from papers presented at the Sixth International Symposium on Chemical Reaction Engineering. Special attention is given to the modelling of single phase reactors, fixed beds, trickle beds, fluid beds, and gas bubble reactors.     

Hollow fiber membrane contactor as a gas-liquid model contactor

Microporous hollow fiber gas-liquid membrane contactors have a fixed and well-defined gas-liquid interfacial area. The liquid flow through the hollow fiber is laminar, thus the liquid side hydrodynamics are well known. This allows the accurate calculation of the fiber side physical mass transfer coefficient from first principles. Moreover, in the case of gas-liquid membrane contactor, the gas-liquid exposure time can be varied easily and independently without disturbing the gas-liquid interfacial area. These features of the hollow fiber membrane contactor make it very suitable as a gas-liquid model contactor and offer numerous advantages over the conventional model contactors. The applicability and the limitations of this novel model contactor for the determination of physico-chemical properties of non-reactive and reactive gas-liquid systems are investigated in the present work. Absorption of CO₂ into water and into aqueous NaOH solutions are chosen as model systems to determine the physico-chemical properties for non-reactive and reactive conditions, respectively. The experimental findings for these systems show that a hollow fiber membrane contactor can be used successfully as a model contactor for the determination of various gas-liquid physico-chemical properties. Moreover, since the membrane contactor facilitates indirect contact between the two phases, the application of hollow fiber model contactor can possibly be extended to liquid-liquid systems and/or heterogeneous catalyzed gas-liquid systems.     

转盘反应器固定米根霉的L－乳酸发酵

研究了米根霉的固定化方法，研制了用吸附法固定米根霉的生物转盘反应器，考察了在该反应器中培养基组成及其它操作条件对Ｌ－乳酸发酵的影响。实验结果表明，应用吸附法固定化的米根霉及生物转盘反应器进行Ｌ－乳酸发酵具有发酵速率快，Ｌ－乳酸得率高及既能用于连续发酵又能用于间歇发酵等优点     

交流接触器温度场仿真及试验验证

将ANSYS有限元热分析应用到交流接触器热特性分析中,模仿其实际工作环境,构建交流接触器三维稳态热分析模型,确定热源、导热系数和表面散热系数,对接触器的稳态温度场进行分析;进一步改变施加的边界条件,研究不同散热方式下接触器的温度分布。最后对CJX2-0910型交流接触器进行温升试验,将温度场的仿真结果与试验结果比较,误差较小,表明所建立热分析模型的可行性。研究结果对接触器材料的选择、结构的设计及其性能的优化有重要意义。