APPLICATIONS OF PNEUMATIC BIOREACTORS IN WASTEWATERS TREATMENT 1. MIXING EFFICIENCY AND DISTRIBUTION IN SPLIT-CYLINDER GAS-LIFT BIOREACTOR FOR VISCOUS MEDIA

2014 ◽  
Vol 13 (10) ◽  
pp. 2653-2664
Author(s):  
Dan Cascaval ◽  
Anca-Irina Galaction ◽  
Ramona Mihaela Matran ◽  
Alexandra Cristina Blaga ◽  
Marius Turnea
Keyword(s):  
Mixing Efficiency ◽  
Wastewaters Treatment ◽  
Viscous Media ◽  
Gas Lift ◽  
Pneumatic Bioreactors

Stirring and Mixing Effects

1998 ◽  
Author(s):  
Irving R. Epstein ◽  
John A. Pojman
Keyword(s):  
Three Dimensional ◽  
Reaction Diffusion ◽  
The Other ◽  
Mixing Efficiency ◽  
Nonlinear Kinetics ◽  
Concentration Gradients ◽  
Overwhelming Evidence ◽  
Perfect Mixing ◽  
Viscous Media

In almost everything that we have discussed so far, we have assumed, explicitly or implicitly, either that the systems we are looking at are perfectly mixed or that they are not mixed at all. In the former case, concentrations are the same everywhere in the system, so that ordinary differential equations for the evolution of the concentrations in time provide an appropriate description for the system. There are no spatial variables; in terms of geometry, the system is effectively zero-dimensional. At the other extreme, we have unstirred systems. Here, concentrations can vary throughout the system, position is a key independent variable, and diffusion plays an essential role, leading to the development of waves and patterns. Geometrically, the system is three-dimensional, though for mathematical convenience, or because one length is very different from the other two, we may be able to approximate it as one- or two-dimensional. In reality, we hardly ever find either extreme—that of perfect mixing or that of pure, unmixed diffusion. In the laboratory, where experiments in beakers or CSTRs are typically stirred at hundreds of revolutions per minute, we shall see that there is overwhelming evidence that, even if efforts are made to improve the mixing efficiency, significant concentration gradients arise and persist. Increasing the stirring rate helps somewhat, but beyond about 2000 rpm, cavitation (the formation of stirring-induced bubbles in the solution) begins to set in. Even close to this limit, mixing is not perfect. In unstirred aqueous systems, as we have seen in Chapter 9, it is difficult to avoid convective mixing. Preventing small amounts of mechanically induced mixing requires considerable effort in isolating the system from external vibrations, even those caused by the occasional truck making a delivery to the laboratory stockroom. It is possible to suppress the effects of convection and mechanical motion in highly viscous media, such as the gels used in the experiments on Turing patterns as discussed in the previous chapter. There, we can finally study a pure reaction-diffusion system. Systems in nature—the oceans, the atmosphere, a living cell—are important examples in which chemical reactions with nonlinear kinetics occur under conditions of imperfect mixing.

Distribution of mixing efficiency in a split-cylinder gas-lift bioreactor forYarrowia lipolyticasuspensions

2014 ◽  
Vol 93 (1) ◽  
pp. 18-28 ◽  
Author(s):  
Dan Caşcaval ◽  
Ramona Mihaela Matran ◽  
Marius Turnea ◽  
Alexandra Cristina Blaga ◽  
Anca-Irina Galaction
Keyword(s):  
Mixing Efficiency ◽  
Gas Lift

Distribution of Mixing Efficiency in a Split-Cylinder Gas-Lift Bioreactor with ImmobilizedYarrowia LipolyticaCells Used for Olive Oil Mill Wastewater Treatment

2015 ◽  
Vol 203 (5) ◽  
pp. 666-675 ◽  
Author(s):  
Ramona Mihaela Matran ◽  
Anca-Irina Galaction ◽  
Alexandra Cristina Blaga ◽  
Marius Turnea ◽  
Dan Caşcaval
Keyword(s):  
Wastewater Treatment ◽  
Olive Oil ◽  
Mixing Efficiency ◽  
Olive Oil Mill Wastewater ◽  
Gas Lift

Ion Beam Mixing of Ni-Ti Bilayered Thin Films

1985 ◽  
Vol 43 ◽  
pp. 290-291
Author(s):  
A. K. Rai ◽  
R. S. Bhattacharya ◽  
M. H. Rashid
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Amorphous Alloys ◽  
Ion Beam ◽  
Ion Bombardment ◽  
High Energy ◽  
Mixing Efficiency ◽  
Ion Beam Mixing ◽  
Enhanced Diffusion ◽  
Binary Metal

Ion beam mixing has recently been found to be an effective method of producing amorphous alloys in the binary metal systems where the two original constituent metals are of different crystal structure. The mechanism of ion beam mixing are not well understood yet. Several mechanisms have been proposed to account for the observed mixing phenomena. The first mechanism is enhanced diffusion due to defects created by the incoming ions. Second is the cascade mixing mechanism for which the kinematicel collisional models exist in the literature. Third mechanism is thermal spikes. In the present work we have studied the mixing efficiency and ion beam induced amorphisation of Ni-Ti system under high energy ion bombardment and the results are compared with collisional models. We have employed plan and x-sectional veiw TEM and RBS techniques in the present work.

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