In this paper a two impinging streams cyclone contacting system suitable for handling of solid-liquid systems has been studied Certain pertinent parameters such as: solid holdup, mean residence time and residence time Distribution (RTD) of solid particles have been investigated A stochastic model based on Markov chains processes has been applied which describe the behavior of solid particles in the contacting system.From this model the RTD data were estimated and compared with the experimental results. The RTD data were obtained at different D t and compared with those estimated from the model. At Dt = 0.362 s a good correlation has been observed between the predicted and experimental data. The RTD data may be used to determine certain pertinent characteristic parameters of physical and chemical apparatuses such as conversion in chemical Reactors.

A mathematical model for the prediction of internal recirculation of complex impinging stream Reactors has been presented. The model constitutes of a repetition of a series of ideal plug flow Reactors and CSTR Reactors with recirculation. The simplicity of the repeating motif allows for the derivation of an algebraic relation of the whole system using the Laplace transform. An impinging streams Reactor system with one axial and two tangential inlet fluid streams was constructed and considered as a case study. The model predicts satisfactorily the complex and flow rate dependent experimental residence time distribution functions obtained employing a pulse tracer method for different total flow rates of the incoming feed. The variation of the controlling parameters with changing the total inlet flow rate are discussed. The presented model can predict complex internal recirculation streams within the impinging streams Reactor system.

This work presents an experimental study dealing with the deviations from the ideal flow models in the case of the flow of ε-caprolactam and, respectively, of the polymer melt, along an industrial unit for polyamide-6 synthesis. The flow pattern was determined by analyzing the mean residence time and dispersion criterion, which were obtained from radiotracer measurements. Different flow types were evidenced for different zones of the industrial polymerization unit plug-flow with small mixing contribution in the Reactor feeding pipe and in the prepolymerizer device and stirred flow with flow defects (stagnant zones and recirculation) for the polymerization column. The analysis of the residence time distribution functions revealed different flow patterns according to different regions of the polymerization column. We estimated the stagnant volume of each polymerization zone by comparing the experimental mean residence time and corresponding nominal residence time, defined as the ratio between the total volume of the zone and the volumetric flow rate. The detection of some important flow anomalies occurring in the 3rd and 4th zones of the polymerization column indicates the positions requiring an improvement of hydrodynamic regime. These experimental results were used and to ameliorate the operating regime of the ε-caprolactam polymerization unit.

The aim of this paper was to present the influence of hydraulic behaviour in the treatment of sewage (domestic wastewater) using panelled anaerobic baffle-cum filter Reactor (PABFR). The PABFR has five compartments of equal size in which the first three compartments operate as anaerobic baffled Reactor (ABR) followed by anaerobic filters (AF). The combined Reactor has a great potential for its application due to its panelled structure and arrangement of baffles inside each compartment. Hydrodynamic behaviour of the Reactor was determined by means of a pulse tracer test and by calculating the residence time distribution curves at different flow rates. At high flow rates [with hydraulic retention time (HRT) <4 h], the mixing pattern in ABR showed a completely mixed type with a maximum dead space of 14 % and as the flow decreased (HRT of 8 and 12 h), the ABR’s mixing behaviour was intermediate between plug flow and completely mixed. In the case of AF, as the flow increased, the dispersion was intermediate between completely mixed and plug flow, and as the flow rate decreased, the Reactor became completely plug flow with the dead space ranging between 2.2 and 7.4 %. On the whole, PABFR treatment performance in terms of chemical oxygen demand removal was 90, 89 and 64 % for 12-, 8- and 4-h HRT, respectively, which clearly shows the correlation between mixing and Reactor process performance. Thus, the outcome of this research in general highlights the importance of hydrodynamic behaviour for a better operation of the Reactor.