Recycling continued

Canadian consumption of recovered paper is about 4 million t/yr, much of it imported from the United States. Paper recycling continues to grow worldwide, particularly in Europe and the Pacific Rim. Worldwide use of recycled paper is expected to increase from nearly 75 million tons in 1988 to 130 million tons in 2001 (58). 

Soil washing is based on the use of water-based leachates, which are recycled continuously in the machine. The end products are a relatively clean, coarser soil fraction and a wash water containing finer soil particles and most contaminants. The small levels of organic contamination remaining in the coarser materials are removed readily with heat. The wash water, depending upon the specific contaminants, responds to various traditional treatment methods, such as bioremediation, air stripping, chemical precipitation, or membrane separation. 

Desorption is carried out by a hydrocarbon compound, whose boiling-point is lower than that of the feedstock, and which is recycled continuously to the extraction section after the separation of olefins. 

A more complicated but also very instructive and versatile process was published by Hydro Quebec, namely, the indirect oxidation of aromatics, specifically naphthalene, by ceric salts [9]. The electrolysis is only a small part of the process Cerous methanesulfonate is oxidized to ceric methanesulfonate. The organic part of the process takes place in a separate reactor The aqueous ceric salt oxidizes the organic substrate in a heterogeneous two-phase reaction that requires good mixing. After the separation of the aqueous and organic phases, the aqueous phase is extracted with a solvent that is recycled continuously. In a follow-up step, organic impurities must be removed from the cerous solution before it is fed back to the electrolysis. The product (naphthoquinone) has to be dried. 

WITHOUT RECYCLE INITIAL RECYCLE RECYCLE CONTINUOUS... 

Gobie, W. A. Ivory, C. F. "Recycle Continuous Flow Electrophoresis Zero Diffusion Theory" AIChE ]. 1988, 34, pp 474-482. 

Many novel electrophoretic devices and techniques have been proposed for continuous electrophoretic separations such as the velocity-stabilized Biostream/Harwell device (9-11), the recycle continuous-flow electrophoresis device (12-14), Bier s isoelectric focusing technique (15),... 

Use crossflow batch with 100% recycle continuous with recycle ratio 15 to 30/1 or multistage (often three stages). Criteria to back wash and clean operate until a given concentration or volume reduction is reached in the retentate or a given purity or volume is achieved in the permeate. 

Use crossflow batch with 100% retentate recycle, continuous bleed with recycle ratio 15 to 30/1 and multistage when a concentrated retentate is desired or when particle diameter <0.1 pm. Criterion to backwash/or clean when 90% reduction in retentate volume is achieved given quality or volume of permeate the permeate flux <15% of initial flux or when the viscosity of the retentate is 100 to 300 mPa s. This corresponds to concentrations for pigments of 30 to 70% for microorganisms of 1 to 10%. 

The second step is the extraction of caffeine. CO2 is first humidified before being passed through the charge of ground coffee. As we have discussed, caffeine is exu acted by the moist CO2. Incidentally, one of the examples states that residual oil, i.e., oil which has not been extracted by dry CO2 in the first step, is also extracted by the moist CO2, which further corroborates the information given in Chapter 10 on the selectivity. The caffeine is separated from the CO2 in another separator vessel. Aroma oil and CO2 recycle continues until all the cal feine has been extracted. 

Figure 3 shows how the PCB contamination of a large quantity of oil is progressively decreased to 42 ppm by changing five cartridges containing 16 Kg each of solid bed. In this experiment, 440 kg of oil containing 4,000 ppm PCB was recycled continuously at 100 L/h at 80° C. 

The procedures where the basic separation mechanism (steric exclusion) remains unchanged (recycling, continuous GPC, differential, vacancy and flat bed techniques). 

Phosphors recycling Continued) alkaline fusion, 192 direct leaching, 188-191 mechanochemical treatment, 191-192 solvent extractirai, 192-194 physical separatirai... 

Use crossflow batch with 100% retentate recycle, continuous bleed with recycle ratio 15-30/1 and multistage when a concentrated retentate is desired or when particle diameter <0.1 gm. 

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