Mixing speed, effect

Variations in viscosity of both the incoming and finished products have a dramatic effect on mixer performance. Standard operating procedures should include specific operating guidelines for the range of variation that is acceptable for each application. The recommended range should include adjustments for temperature, flow rates, mixing speeds, and other factors that directly or indirectly affect viscosity. 

Reactor Conditions for Experimental Runs. Operating conditions for the continuous, stirred tank reactor runs were chosen to study the effects of mixing speed on the monomer conversion and molecular weight distribution at different values for the number average degree of polymerization of the product polymer. 

Initial comparison of CFSTR runs with similar feed conditions indicates conditions for which the monomer conversion may be dependent on mixing speed. However, when the effects of experimental error in monomer conversion and differences in reaction temperature are considered, the monomer conversion is seen to be relatively independent of mixing speed for rpm equal to or greater than 500. Comparing Run 14 with Run 12 reveals a small decrease in monomer conversion in spite of a rise in reactor temperature of 2°C. This indicated the presence of a small amount of bypassing or dead volume at the lower mixing speed. This imperfect mixing pattern would also be present in Run 15. 

To differentiate between the micro-mixed reactor with dead-polymer and the by-pass reactor models in this investigation, the effect of mixing speed on the value of "( )" was observed. As illustrated in Table V, the value (j>" is not observed to increase with decreasing mixing speed as would be expected for a by-pass reactor. This rules out the possibility of a by-pass model and further substantiates the dead-polymer model. 

The mixing speed had little or no signficant effect on the monomer conversions or the shape of the molecular weight distributions for mixing speeds of 500 rpm or greater. 

In Example 2.12, the method of random balance, factors have been selected by the effects of their significance on dynamic viscosity of uncured composite rocket propellant. The screened-out factors are X3 mixing speed X5 time after addition of AP and Xg vacuum in vertical planetary mixer. Since insufficient vacuum in a mixer causes bubbles to appear in the cured propellant, the value of this factor is fixed at the most convenient one. For the other two factors a design of basic experiment has been done according to a FUFE matrix, as shown in Table 2.103, and aimed at obtaining the mathematical model of viscosity change. 

Chin, N.L., and Campbell, G.M. (2005). Dough aeration and rheology. II. Effects of flour type, mixing speed and total work input on aeration and rheology of bread dough, J. Sci. Food Agriculture 85 2194-2202. 

The use of small particles results in high catalyst utilization, but the particles are subjected to attrition. Filtration is an energy intensive aftertreatment, therefore an optimum particle size is sought with respect to catalyst effectiveness, settling and mixing speed. In these well-stirred reactors a good heat supply or removal is achieved. 

Different mixing speeds were used to see the effect of mechanical forces on the emulsion properties. As expected, at high speed (11,000 rpm), average particle size obtained was smaller than at low speed (7,000 rpm) and the viscosity was higher, as expected (see Table I). The lowest viscosity was not observed at the lowest mixing speed, however, but at 9,000 rpm. This surprising result is discussed later. 

Figure 7.34. Typical rcstilte with a wcH-mixcd reactor, showing the effect of mixing speed.

The effects of palladium metal oxidation states, palladium metal dispersion and other properties on catalyst performance are discussed in this paper. Results on the effects of reaction conditions on the reaction rate, such as mixing speed, reaction temperature, solvent and feed impurity, are presented in this paper as well. 

Without further analysis, these results add little to what we have already seen. Nevertheless, we notice that the estimates of the effects are of the same order, with three important exceptions, the inversion of the coefficient supposed to represent the effect of the extrusion speed, considerable changes in the mixed interaction effect fe 14.25, and also a difference in the constant term b g (figure 3.15). 

Figure 14.13 Effect of DCP concentration (phr) on viscosity for EB75PP25 blend cure at 200°C (mixed speed 60 rpm) ( ) 0.00 (O) 0.33 (A) 0.67 ( ) 1.00 (A) 1-33. (From Reference 24 with permission from John Wiley Sons, Inc.)...

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