Scale mixing

Figure 7-17. Mixing scale-up factors referenced to experienced ratios of power per unit volume. (Source Penny, N. R Chem. Engr., p, 88, March 22, 1971.)...

A consequence of cathodic protection in seawater is the formation of a protective calcareous scale . The increased local pH at the steel surface caused by hydroxyl production (a product of the cathodic reaction) favours the deposition of a mixed scale of CaCO, and Mg(OH)2. This scale is beneficial since it is protective and non-conducting, thus reducing the cathodic current density. Ensuring a high current density in the early period of operation will encourage calcareous scale deposition and thus reduce the current requirements in the long term (see Section 10.1 Principles of Cathodic Protection ). 

This is an important consideration in the selection of an optimum polymerization diluent, which is very easily neglected in laboratory investigations. Also, since little is known cd>out particle coalescence in the presence of mechanical agitation, extreme care must be taken in mixing scale-up. 

Still, the strain enthalpy is of particular importance. An elastic continuum model for this size mismatch enthalpy shows that, within the limitations of the model, this enthalpy contribution correlates with the square of the volume difference [41,42], The model furthermore predicts what is often observed experimentally for a given size difference it is easier to put a smaller atom in a larger host than vice versa. Both the excess enthalpy of mixing and the solubility limits are often asymmetric with regard to composition. This elastic contribution to the enthalpy of mixing scales with the two-parameter sub-regular solution model described in Chapter 3 (see eq. 3.74) ... 

John A. Von Essen. Liquid mixing scale-up procedures. Presented at Inter-American Congress and VII Chilean Congress of Chemical Engineering, Santiago, Chile, Nov 6-11, 1983. 

It is interesting to note that in a study by A. P. Mirabel and A. S. Monin, written after Ya.B. s paper, the expression for the turbulent diffusion coefficient in a two-dimensional turbulent field differs from the one obtained by Ya.B. by a factor which is equal to some logarithmic power of the ratio of the mixing scale to the energy-supply scale. 

Reprinted with permission from J. Y. Olclshue, Mixing Scale-Up Techniques Biotech. Bioeng. 8 (1966) 3—24. 1966 by John Wile Sons. Inc.. New York. NY. 

The yield of near-resonant four-wave mixing scales as... 

Similarly, when moving from the pilot plant to manufacturing, a process engineer will either choose an existing vessel or specify the design criteria for a new reactor. A necessary condition for operation with a specified reactor temperature profile is that the required jacket temperature is feasible. We have therefore chosen to focus on heat transfer-related issues in scale-up. Clearly there are other scale-up issues, such as mixing sensitive reactions. See Paul [1] for several examples of mixing scale-up in the pharmaceutical industry. 

Oldshue, J.Y. "Fermentation Mixing Scale-up Techniques", Biotech, and Bioeng. VIII (1),3 (1966). 

Mixing Scales. A stochastic simulation will generate C (t,x,y) for a unit inlet concentration in a two-dimensional flow field. The goal oi this generation is to deduce the behavior of the dispersivity and relate these back to the statistical properties of the field however, there are two ways to do this each manifesting a particular scale of mixing. 

Coating suspension preparation is critical to successful and consistent coating. The suspension must be free of air and uniformly mixed. Selection of tank geometry is important to achieve suspension homogeneity. Long tall vessels that minimize the exposed surface are preferred. Some polymers require low shear mixing. Scale-up should include evaluation of mixer speed, suspension preparation, and hold times at both the development and the launch sites. 

As a final consideration, it is relevant to discuss the behaviour of mixtures of different plastics. In fact, one possible process for recovering valuable chemical and petrochemical products from plastic waste is the stepwise thermal degradation of polymer mixtures. This potentially allows the step-by-step simultaneous separation of the different fractions generated by the polymers of the blend. The effect of the mixing scale of PE and PS and their interactions in the melt on the basis of several hypotheses was recently investigated (Faravelli et al., 2003). The first and simplest approach was a completely segregated model which... 

Oldshue, J. Y., Fermentation Mixing Scale-Up Techniques, 5/otecA, Bioeng., VIII 3-24 (1966)... 

Equation (13.10) is demonstrated in Fig. 13.8, which shows the experimental mixing rate d(4Dt) / d

linear relationship indicates that the amount of mixing scales with AHmiJAHcoh and that (13.10) provides a reasonable prediction of the ion beam mixing rate in metal/metal bilayer systems irradiated with heavy ions at low temperatures. 

Reprinted with permission from J. Y. Olclshue, Mixing Scale-Up Techniques Biotech. 

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