Impurities rejection

The sequence of process operations for coal agglomeration is depicted in the generalized flow diagram of Fig. 8.2. Possible equipment for each step is also indicated. In general, equipment well-known in the chemical and mineral industries can be applied in the process. The operations consist of selective flocculation or microagglomeration, agglomerate recovery with simultaneous impurity rejection, further size enlargement of the recovered and... 

SPAGIRUS — Any man who can separate the true from the false, set the good apart from the bad, and the pure from the impure, rejecting duality and cleaving to unity. 

Stage Ratio Recovery (%) Impurity (%) Impurity (%) Rejection (%) (L/m h)... 

The material balance for the first cycle of operation in the present study is shown in Figure 42.12. The present material balance shows a total input of 12 m of 10% NaSCN feed containing 3% impurities. A total amount of 18.4 m of DM water is added for dilution of feeds during the five stages from cycle 2 onwards. The ouqDut product is 21.6 kg of 3.6% NaSCN, which is fi ee of color and contains only 0.06% of impurities since a dilution of 1 1.5 is employed from Stage II onwards. The other output is a final reject quantity of 4.8 m containing <0.1% NaSCN and 4.7% impurities for disposal. The total NaSCN recovery is 99.4% and impurity rejection 94.2%. 

Another key variable in batch cooling is seeding. The difficulty is in determining the seed point, which is ideally when the batch temperature first crosses the saturation curve. However, this temperature can be affected by batch-to-batch variations in several factors, including the actual concentration of the material to be crystallized, as well as by impurities that can affect the solubility. If the seed is added at a temperature above the solubility temperature, some or all of it can dissolve, resulting in uncontrolled nucleation. If the seed is added at a temperature too far below saturation, the product may have already nucleated. In either case, the increase in nucleation could result in a decrease in impurity rejection and/or a change in particle size distribution and other physical attributes. 

For solvent systems with a window of operating temperature, proper selection of the method of supersaturation generation (e.g., cooling and antisolvent addition) and mode of crystallization (e.g., batch vs. semicontinuous) can also affect the overall crystal growth rate. In many instances in which solvent or impurity rejection becomes critical, adequate mixing to avoid local high supersaturation can be critical. Examples 9-2 and 10-4 illustrate two cases of rejection of impurities and residual solvent. These examples show how various means are applied to overcome these complications. 

Pictures of the crystals obtained by this procedure are shown in Fig. 7-14. Filtration rates and impurity rejection are satisfactory. Scale-up from the pilot plant to manufacturing scale (10,000 liters) resulted in no significant differences in crystallizer performance. ... 

Impurities rejection for solid crystallized with the impinging jets was good at 25°C and excellent at 50°C. For an undesired contaminant required to be <0.5 wt%, the impinging jet operation at 50 C... 

Additive and impurity rejection at the growing crystal front leads to uneven distribution in a crystalline polymer. This redistribution process has been studied by UV and fluorescence microscopy and by an electron microscope with energy dispersive x-ray analysis. In polymer samples which are quenched after rapid crystallization, the additive distribution is kinetically determined and may be modeled in a computer as a three-dimensional zone-refining process. In annealed polymer samples, low molecular weight additives are uniformly concentrated in the amorphous phase. The additive distribution reflects that of crystalline material within the polymer. Antioxidant and uv stabilzer redistribution probably does not have a major effect on polymer stability, but the redistribution of partially oxidized, impure polymer may be important... 

The acid and alum salt used in the above treatment must be carefully examined for the presence of arsenic, and any deliveries of either article, which contain that impurity, rejected. 

During the solidification process the impurities rejected in the liquid are allowed to diffuse. However due to the competition betv7een growth and diffusion the accumulate in a layer of thickness Dj /v, called coherence length" (see the upper left part of Fig.11). The melting point of a dilute alloys depends on the... 

The effect of feed concentration on flux and rejection is depicted in Fig. 4.17. As expected, a rise in the feed concentration resulted in a decrease in flux and percentage of impurity rejection. This is due to increase in concentration polarization and osmotic pressure at the membrane surface. Higher solute concentrations at the feed side induce an osmotic pressure gradient, which... 

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