A class of discontinuous dynamical systems II. An industrial slurry high density polyethylene reactor

A lumped parameter model of an industrial HDPE reactor is presented. Discontinuity in the mode of operation makes either a set of 15 DAEs or a set of 12 DAEs applicable to this system at any instant. The reactor switches back and forth from one model to another reaching a time averaged steady state. The DAEs are integrated by DASSL. Using the Box-Complex procedure, the sum of squares of errors between plant data and model prediction is minimised and the model tuned. The tuned parameters agree with the literature values. Sensitivity analysis of the model shows that manipulation of pressure will yield a faster change in the reactor conditions as compared to manipulating the catalyst feed rate. (C) 2001 .

Combined surface and viscous flow of condensable vapor in porous media

The transport coefficient of cyclohexane vapor in an activated γ alumina pellet, estimated using the transient response method on a thermogravimetric analyzer (TGA), is reported as a function of relative saturation. An extended hydrodynamic model is proposed to account for the combined surface and viscous flows in coexisting adsorbed and capillary condensed phases, respectively, in a porous solid with a distribution of pore sizes. The structural features reflected in the isotherm data, as well as in the concentration dependence of the overall diffusivity, are well represented by the proposed model. The results are compared with the earlier hydrodynamic model. The model is also applied to published data, and anomalous trends reported in the literature are discussed

Interrelationship between electrocoalescence and interfacial tension in a high acidity crude: Effect of pH and nature of alkalinity

The efficacy of electrocoalescence is critically dependent upon the interfacial tension of the crude-water interface. This study demonstrates the effect of interfacial tension on the electrocoalescence efficiency in crudes with high acidity. The interfacial tension is estimated using spinning drop tensiometer (SDT) and electrocoalescence experiments are performed at an electric field = 1.15 kV(rms)/cm at a frequency of 50 Hz. It is observed that separation of water from the crude is hindered at high pH for two very different reasons depending upon the source of alkalinity. Calcium hydroxide induced alkalinity leads to more rigid interface, resulting in delayed electrocoalescence. On the other hand, sodium hydroxide based alkalinity leads to ultra-low tension of crude-water interface, thereby causing oil-in-water emulsion. Increase in the pH also leads to poor quality of brine resolution, in case of sodium hydroxide based alkalinity (pH = 10) we get unresolved turbid emulsion