Cascade recycle

Fig. 7 Concept of repeated partial recycle (cascade recycle) of lightweight concrete...

Pan granulation of ammonium nitrate also has been developed commercially (16,17). Essentially water-free melt (<0.5%moisture) is sprayed onto a cascading bed of fines (usually cmshed recycle) ia a tilted, rotatiag pan. Production of 18—20 t/h is common. Product made ia this manner is said to require ao conditioning. The pan is an excellent size classifier, making it easy to produce granules of any desired size from 1 to 11 mm diameter. 

Cascade with recycle required to obtain one (relatively) pure permeate and enriched retentate. 

Typically, the saponification is run with 10% sodium hydroxide solution in a reactor cascade at 95-98°C under stringent pH control. The saponification mixture is separated in a settler. The upper phase consists of alkanes with a small proportion of chloroalkanes, which is removed by oleum refining or dehydrochlorination and high-pressure hydrogenation. The refined alkanes can be recycled to the reactor. In the aqueous lower phase are alkanesulfonates, sodium chloride, and between 4 and 8 wt % hydrotropically dissolved alkanes. An optimal separation can be approached at 95 °C, and residence times of less than 60 min if Fe(III) ions are added and pH values of 3-5 are maintained. 

For chemical recycling of plastics refuse, a cascade of cycled-spheres reactors was developed which combined separation and decomposition of polymer mixtures by stepwise pyrolysis at moderate temps. In low-temp, pyrolysis, mixtures of PVC, PS and PE or PS, polyamide-... 

Although the catalysts do not interfere with each other, the immobilization process resulted in higher yields and ees than with the raw enzyme the initial activity was over five times greater. Additionally, the biocomposite with enzyme was able to be recycled and maintained its activity, which demonstrates the utility of such an immobilization system for potential cascades with mutually interfering catalysts. 

Mann, U., Rubinovitch and Crosby, E. J., Characterization and Analysis of Continuous Recycle Systems Part II. Cascade, AIChE J., 27 829-836 (1981)... 

Catalytic methods, chemo- as well as bio-catalysis, are of vital importance in the conversion of natural products into derivatives (semi-synthesis). In chemo-catalysis conventional catalysts, such as mineral acids, are being replaced by recyclable solid catalysts. Further progress is also expected in cascade processes in which synthesis steps are combined to one pot methods. 

Effective and simple immobilization of enzymes can be obtained by the cross-linking of enzyme aggregates, so-called CLEAs [55]. In this way, essentially any enzyme, including crude preparations, can be transformed into a heterogeneous type of material, insoluble in both water and organic solvents, that is stable and recyclable with high retention of the enzyme s original activity [56], These enzyme preparations are, therefore, of special value for both bio-bio and bio-chemo cascade processes. 

The countercurrent (recycle) cascade (Fig. 8.3) is much more useful because by reprocessing the waste stream a larger fraction of the desired isotope is recovered. In a recycle cascade the i th stage is fed by a mixture of the product, Y( i) from the (i — l) th, and the waste, X(i+ X) from the (i + l) th, stage. A distillation column... 

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