Table 1 — Conditions of different quartz sand particles
Related Figures (10)
Table 2 — Quantities of three examined static mixers Fig. 2 — Different types of mixing elements must be evaluated. The smaller the number of mea- surements, the more indeterminate the value for ho- mogeneity. If the system variance is chosen as a mea- sure for comparing the mixing quality’, the sample granulation is irrelevant, since the system variance is independent of its influence. According to Boss two to forty samples, taken from a mixture, give the cor- rect information on the homogeneity. We have di- vided the whole mixture into eight individual samples and the results have shown high reproducibility for mixtures of model material (Figure 4. each value is a mean of eight samples). Hersey'? has defined an or- dered mixture as having zero standard deviation of the sample concentration at all sample sizes, provided that the sample size is greater than the size of a single order unit, as opposed to a random mixture, where the standard deviation decreases with increasing of the sample size. Static mixers in general do not show traces of segregation, which is their main advantage. Some investigations have shown that segregated islands may exist in the flow'*. They may give a better quality mixtures in the beginning before the flow is stabilized, but there is more material to be mixed, and the longer the process lasts the better the qual- ity is and the better the mixture is stabilized, which is the reason why these types of mixing devices ig. 8 — Statistical parameters for Kenics type mixer, with components A and D mixed in 1:3 ratio
