Mean slurry concentration

Effect of Drum Speed on C/C. As a result of the slip velocity between the particles and the fluid, the mean solids concentration in the drum is higher than that in the feed. Figure 27 shows the mean slurry concentration in the drum... 

Means should be provided for measuring and varying the slurry concentration in the contacting zone up to 50 % by volume. 

The pK of Ca2+aq (204), 12.6 at zero ionic strength, rising to over 13 as ionic strength increases, means that concentrations of CaOH+aq will be negligible in body fluids (lpolluted waters, and under all conditions of biological relevance, from the very low pHs of 0.5 (Thiobacillus thiooxidans) to 1.5 at which bacteria used for oxidative metal extraction operate (205), through acid soils and acid rain (pH 3 to 6), streams, rivers, and oceans (pH 6 to 8), soda lakes (pH 10), up to the pHs of 11 or more in Jamaican Red Mud slurry ponds (206) (cf. Section II.C.l below). 

In general, the rule of thumb is to add the diluting component to the abrasive component. There are, however, exceptions to this rule of thumb, so experience and the recommendations of the slurry manufacturer should be considered. In the case of silica-abrasive oxide-polishing slurries, this means slurry first, water second. Even when practiced in this manner, slurry diluted at the user site will typically have more agglomerates than slurry diluted to use-concentration by the slurry manufacturer. The primary reason... 

Approximate detection limits were calculated from the mean absorbance and relative standard deviation values obtained for each spinach slurry concentration, and the results are presented in Table 7.1. Although the values cannot be directly compared as they have been calculated at different absorbance values, and they do not represent true detection limits as the concentrations used are too high owing to the level of lead in the spinach sample used, they clearly indicate that an increase in spinach concentration allows lower detection limits to be achieved. 

Effect of Feed Flow Rate on Slurry Hold-up. Figure 25 depicts the effects of the drum speed, and slurry feed concentration on the slurry mean solids concentration in the drum for the same conditions given in Figure 24. The mean slurry solids concentration in the drum varied significantly with the drum speed for the slurry feed solids concentrations of 3.5% and 7.5%, whereas a small variation in the mean solids concentration occurred for a slurry feed solids concentration of 45.8%. For... 

Figure 25. Effect of drum speed on slurry mean solids concentration in a drum without lifters.

Slurry Hold-up and Mean Solids Concentration. Figure 30 depicts the influence of the drum rotational speed on the slurry hold-up for slurry feed concentrations of 7.8%, 21.0%, and 45.9%. The slurry hold-up-drum speed relationship exhibited a minimum for all the feed solids concentrations examined. At low drum speeds, the slurry hold-up increased with the feed solids concentration. However, at high drum speeds the effect of the slurry feed solids concentration on the slurry holdup was less significant. The most important aspect of Figure 30 is that the lifters eliminated the abrupt changes in the slurry hold-up observed for the drum without lifters. 

Figure 31 demonstrates the effect of the drum speed on the mean solids concentration in the drum for the same conditions as in Figure 30. For the cases of Cp = 21.0% and 45.9%, the hold-up solids concentration decreased with the drum speed. However, for the case of Cp = 7.8%, the hold-up mean solids concentration was independent of the drum speed. At a given drum speed, the slurry mean solids concentration in the drum increased with Cp.

The results shown in Figures 25 and 31 indicate that for a given Cp the mean solids concentration in the drum with lifters is lower than that for the drum without lifters. This trend is due to higher axial particle velocities encountered in drums with lifters. For the drum with lifters, the variation of the slurry mean solids concentration with the drum speed was much less pronounced than that observed for the drum without lifters. Also, the effect of Cp on the hold-up solids concentration was more pronounced for the drum with lifters. 

C Slurry mean solids concentration in the drum hold-up, vol. %... 

Feed slurry concentration s = 1 10 % w/w Mean particle size = 1 ->500 pm Mass of solids processed = 0.5->7500 kg Minimum cake thickness = 5 mm... 

Mean transport concentration of solid particles in the slurry mixture Volrrme fraction of solid particles in the slurry mixture Weight fraction of solid particles in the slurry mixture Volrrme fraction of solid particles in the slurry mixture at level y ... 

Many factors influence the accuracy of experimental data and each experimental run could be described by a different set of parameters n, K, Ty. Since the flow models strongly depend on input data and their evaluation, a sensitivity analysis was used to find effect of value of flow behaviour index n on accuracy of laminar and turbulent flow models. Dependency of slurry/water pressure gradient ratio i / io on mean slurry velocity V of the measured slurries for both tested turbulent models and yield power-law model is shown in Fig. 4, where also a role of parameter n is illustrated. The value of n given by best fitting of laminar data by Eq. (4) represents quite well laminar region. For turbulent data it is not valid (see dashed line). The best fitting value n for turbulent data varies not only with kind of solid material, but depends also on concentration. 

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