Explaining characteristic azeotropic behaviour

An explanation of the formation of minimum-boiling, maximum-boiling and saddle-type azeotropes is given (with illustrative examples) in terms of the molecular interactions in the solutions and in the pure liquids. “Interaction weakening” and “interaction strengthening” effects are defined which tend to be associated with the formation of minimum-boiling and maximum-boiling azeotropes respectively. As defined these effects correspond respectively to positive and to negative values of the interchange energy in regular solution theory, though the concept is considered to be of more general application than is this simple model. When more than two components are present it is possible for both effects to occur leading to the possibility of saddle-type azeotropy.By considering the nature of the intermolecular fones it is possible to predict the kind of azeotope which will be formed, if an azeotrope is formed at all. Although present knowledge of intermolecular fones is far from complete, enough is known to enable this prediction to be made in many cases. The more exacting question of whether or not an azeotope will be formed cannot yet be answered with the same certainty partly because of the lack of a completely satisfactory model of the liquid state.     

Competitative adsorption of two dissolved organics onto activated carbon—II: Adsorption kinetics in batch reactors

Bi-solute adsorption of dissolved organics by activated carbon was studied in a finite bath system. The batch tests with strongly adsorbable species show that at low concentrations (X < 0.1 mmol/1) only external mass transfer resistance is rate-determining. For higher concentrations internal mass transfer becomes increasingly important. This behavior indicates that the diffusional process within the particle occurs predominantly in the adsorbed phase.Bi-solute calculations were performed, using only single-solute data. Systems with differing equilibrium behavior, but similar diffusive properties of both solutes, were described adequately by a model which takes into account diffusion in the liquid-filled pores and in the adsorbed phase, as well as external mass transfer. Deviations between measured and predicted rates can be observed for systems with large differences in the mobility of the diffusing molecules, or if counter diffusion inside the particles occurs. It is likely that the discrepancies in these cases are caused by diffusional interactions between the two different species in the adsorbed phase.     

GRIP: A problem-oriented language

GRIP (GeneRal Interactive Processor) is a problem-oriented language which establishes a powerful and convenient communication linkage between engineer and computer. GRIP is implemented in a set of programs which provide its capabilities for command translation, on-line programming and small database management. The GRIP application program, written using the grammer of the language, provides access to one or more task specific programs and to utility resources such as numerical methods and interactive graphics packages. This paper describes the structure and function of GRIP applications which support chemical engineering education and research activities.     

Studies of structure in carbonized composites from a phenolic resin and oxidized PAN fibres using chromic acid as an etchant

Composites have been prepared from a phenolic resin (49 vol%) and oxidized PAN fibres (51vol%) with heat treatment to 423, 573, 873, 973, 1073 and 1173 K. Optical and scanning microscopy of polished surfaces indicate a fusing of these two materials into a homogeneous matrix. However, SEM of samples etched with chromic acid shows that the identity of materials is preserved. Initially the resin is less reactive than the PAN fibres. Upon carbonization, the carbon from the resin and the PAN have approximately equal reactivities. Enhanced etching occurs at the curved interfaces of the two carbons. The transverse sections of PAN fibres, HTT>973 K exhibit selective etching suggesting the existence of skin/core components in the fibre. It is the more graphitic components of the skin region which are oxidized preferentially.     

地区电网无功电压优化运行与安全控制

针对地区电网(开式电网)的无功电压控制,从全电网的角度阐述了利用调度自动化系统的“四遥”功能,实现地区电网无功电压优化运行集中实时闭环控制的原理和方法,以及控制过程中的安全策略,并以“泰州城区(海陵、高港两区)电网无功电压优化运行集中控制系统”为实例说明了该理论在实际系统中的应用。     

非结构网格上求解中子输运方程的并行流水线Sn扫描算法

间断有限元离散纵标方法(Sn)是广泛应用于求解高维非定常中子输运方程的数值方法,它涉及几何网格空间、速度相空间和中子能群的离散,计算量很大．该文基于非结构网格,提出了基于区域分解的并行流水线Sn扫描算法,通过设计具有不同内在并行度和通信面体比的区域分解方法和队列插入算法,对两个不同物理模型,分别使用两台并行机的92个和256个CPU,获得72倍和78倍以上的加速．可扩展性能分析表明,算法的性能非常依赖于并行机的点对点通信延迟．