Mixer comparisons

V-mixer - comparison with conventional nozzle mixer... 

The reactor parameters shown above are typical for commercial stirred alkylation units in H2S04-butylene service. It is important to emphasize that the mixer comparison was made at constant power. 

Previous investigators such as Albright et al (5) have shown that alkylation catalyst composition has a profound effect on product quality and that quality comparisons must be made at constant catalyst composition. In addition to measurement of product quality differences, one of the objectives of the mixer comparison was to look at possible differences in catalyst composition between the two mixer styles and the subsequent effect on catalyst life. 

The consistency of the raw catalyst composition data can be seen by looking at the bottom part of Figure 5. This is a plot on the sum of wt. % H2SO4, wt. % H2O and wt. % acid soluble oil for each of the acid analyses in the mixer comparison study. The absolute difference between this sum and 100 gives a measure of the consistency of the acid analyses. Except for the one point at about 250 hrs. (and the analyses that were rerun at L75-100 hrs.), the sums in Figure 5 for the mixer comparison runs vary between 99% and 101% with most sums being closer than 1%. If it is considered that these sums are formed from the results of three independent analyses, it can be said that the quality of the acid composition data is very good. 

In a "dying acid" type of experiment with no additions/with-drawals, the fresh acid replacement rate has no real meaning. Values calculated for the mixer comparison data are called equivalent replacement rates. These equivalent replacement rates are the rates necessary (i.e., for a given diluent formation rate) to maintain equilibrium in a hypothetical steady state alkylation unit which uses fresh acid at 98% titratable acidity and spends its acid at the acid strength in question. 

Numerical Simulation of Pipeline Tee Mixers Comparison with Data, in [0.20], p. 141-143... 

Forney, L. J., and L. A. Monclova (1993). Numerical simulation of a pipeline tee mixer comparison with data, presented at the AIChE Meeting, St. Louis, MO. 

Fig. 31. Comparison of mixing rates with different static mixers A, Lightnin B, Komax C, Etoflo HV D, Kenics E, SMXL E, Hi-Mixer and G, SMX.

A practical method of predicting the molecular behavior within the flow system involves the RTD. A common experiment to test nonuniformities is the stimulus response experiment. A typical stimulus is a step-change in the concentration of some tracer material. The step-response is an instantaneous jump of a concentration to some new value, which is then maintained for an indefinite period. The tracer should be detectable and must not change or decompose as it passes through the mixer. Studies have shown that the flow characteristics of static mixers approach those of an ideal plug flow system. Figures 8-41 and 8-42, respectively, indicate the exit residence time distributions of the Kenics static mixer in comparison with other flow systems. 

Mixer Production Cost Comparison for Composite Propellants ... 

Static mixers are typically less effective in turbulent flow than an open tube when the comparison is made on the basis of constant pressure drop or capital cost. Whether laminar or turbulent, design correlations are generally lacking or else are vendor-proprietary and are rarely been subject to peer review. 

Figure 1.19 Semi-analytical calculation of the speed of mixing in an advanced interdigital micro mixer, named SuperFocus, and comparison with previously developed interdigital micro mixers [120],...

Figure 4.39 Comparison of benzal chloride hydrolysis performed in a slit-shaped micro mixer and in a mixing tee [46],...

OS 1] [R 20] [P 1] A comparison of the selectivity/conversion behavior of an interdigital micro mixer-tube reactor with that of a mixing tee of about 1.5 mm inner diameter (and thus of larger internal dimensions) was made (Figure 4.39). For all data gathered, the performance of the micro mixer was much better, e.g. about 30% more selectivity at a given conversion [46]. 

OS 34] [R 17] [R 19] [R 26] [P 24] A detailed comparison of micro mixers from different suppliers and of different mixing principles, with regard to conversion, isomer formation and consecutive nitration, is given in [98]. 

Figure 5.29 Special-type multi-purpose micro devices and mixing tee used for investigation of CO2 absorption. Comparison of their reactor performance as a function of the residence time. Micro bubble columns ( ) 1100 pm x 170 pm, (A) 300 pm x 100 pm and (T) 50 pm x 50 pm Interdigital mixer ( ) (40 pm) caterpillar mixer (A) (850 pm ramp) mixing tee (0) (1 mm) [5],...

For comparison purposes, the results of the various analyses and risk estimates for the mixers/loaders/applicators in greenhouses are summarized in Table 6. All of these analyses present the risk assessor with some information about the possible hazards to workers who are exposed to... 

Table 6 Comparison of Exposure and Risks for Greenhouse Mixers/ Loaders/ Applicators...

The design of a study by Davies et al. (1982) for mixers and applicators was similar to that of Nigg and Stamper (1983). "Between-days" variances of exposure were not given. Mean urinary metabolite concentrations were used to show reduction of internal exposure by protective clothing. The design of the study by van Rooij et al. (1993) was similar to our study (i.e., "within-worker" comparisons of internal exposure). Because no potential dermal exposure was assessed in this study, "within-worker" variances of potential exposure are not known. 

Ritala, M., Jungersen, O., Holm, P., Schaefer, T., and Kristensen, H. G., A Comparison Between Binders in the Wet Phase of Granulation in a High Shear Mixer, Drug Development and Industrial Pharmacy, 12 (11-13), 1685-1700, Marcel Dekker, Inc. (1986)... 

A further development from ADD methods is the use of spiral mixers by small bakers. These machines put energy into the dough less rapidly than the sort of mixer used in the Chorleywood process but a spiral mixer is less expensive and more versatile. The actual dough development time will always depend on the recipe, the flour improver and the flour but, for comparison, while a Chorleywood mixer will develop a dough in 2-5 min a spiral mixer will take 8-15 min. 

Another comparison is due to Van Wageningen et al. (2004) who performed a similar study (in terms of the numerical scheme used) on unsteady laminar flow in a Kenics static mixer. They found that the LB code was 500-600 times faster than FLUENT in terms of simulation time per grid node per time step and that FLUENT used about 5 times more memory than LB. 

Comparison ofthe Plant Concepts To be able to compare the pipeless plant concept with the existing multipurpose batch plant, a reference plant was modelled using PPSiM. In the existing plant three conventional batch mixers work in a shifted parallel fashion. The three batch mixers were modelled by three stations and equipped with all technical functions necessary for the production of all recipes. Therefore each batch could be processed at one of the stations and the vessel transfers were limited to the transportation of empty or loaded vessels. All the other parameters of the model, e.g., charging mass flows, the durations of vessel cleanings and the recipes remained unchanged. 

Fig. 22 Static mixer reactor for two-phase process Comparison with conventional stirred tank...

Besides the two main characteristics of sensitivity as well as specificity of a sensor, the industrial, military, and other standards demand the device to be portable, economical, autonomous, and power efficient. In order to address some of these characteristics, the authors in their respective laboratories have been working on improving the design of the prototype, as shown in Figs. 15.6 and 15.7, respectively. The necessaiy electronics consisting of local oscillators, beat oscillators, smaller cavities, mixers, and phase-locking loops have been assembled in prototypes. As of this date the device needs further evaluation in an operational environment to establish a set of encyclopedic data and for comparison with unknown toxins. 

Fig. 11 Overall reaction rates obtained with static mixers and carrier materials in comparison to the reaction rate without mixing T = 50°C, pui = 5bar, Vaq = 300mLmin , Forg = 50mLmin , Vpeed = 3.0mLmin" Vh2 = lOOmEmin ...

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