Recycling closed loop

Closed-Loop Recycling reclaiming or reusing wastewater for non-potable... 

J. Dingenen and J. N. Kinkel, Preparative cliromatograpliic resolution of racemates on chiral stationary phases on laboratoiy and production scales by closed-loop recycling cliromatography , J. Chromatogr. 666 627-650 (1994). 

C. M. Grill, Closed-loop recycling with periodic intra-profile injection a new binary preparative cliromatograpliic technique , J. Chromatogr. 796 101 -113 (1998). 

Closed-loop Recycling with Periodic Iiitra-proflle Injection (CLRPIPI)... 

Chemical recycling of nylon-6 carpet face fibers has been developed into a closed-loop recycling process for waste nylon carpet.5 The recovered nylon-6 face fibers are sent to a depolymerization reactor and treated with superheated steam in the presence of a catalyst to produce a distillate containing caprolactam. The crude caprolactam is distilled and repolymerized to form nylon-6. The caprolactam... 

In recent months, three nylon producers (DMS, DuPont, and Honeywell) have developed closed-loop recycling processes for nylon carpet,15 thereby joining companies like BASF, Allied, and Rhodia, which have been recycling nylon on a modest level for years. DuPont is building a demonstration plant in Maitland, Ontario, which will be dedicated to the chemical recycling of nylon-6,6 and nylon-6. The newly developed ammonolysis process invented by DuPont can be used to depolymerize both nylon-6 and nylon-6,6. However, the cost of recycled nylon is estimated to exceed that of virgin nylon by ca. 25%. 

Closed-loop recycling processes, 534 CLTE. See Coefficient of lineal- thermal expansion (CLTE)... 

The Vinyloop process is based on the selective dissolution of PVC used in composites applications like cable insulation, flooring, tarpaulins, blisters, etc. After removal of insoluble parts like metals, rubber or other polymers, the PVC is reprecipitated with all additives by introduction of a non-solvent component whieh will form with the seleetive solvent an azeotropie mixture. By using typical conditions, the process is able to reeover a pure PVC eompound powder ready for use without any additional treatment like melt filtration or a new pelletisation (speeific characteristics of the powder are average diameter of 400 microns and bulk density above 600 kg/ eub.m). All the solvents used are eompletely reeyeled and reused. PVC compounds recovered in the Vinyloop process can be reused in a closed-loop recycling scheme... 

CLOSED-LOOP RECYCLING PROCESS FOR PVC IS BASED ON SOLVENTS... 

CLOSED LOOP RECYCLING OF HIGH PERFORMANCE ENGINEERING RESINS... 

Recycling of glass fibre-reinforced plastics is reviewed, with special emphasis on remelting of thermoplastic composites, mechanical recycling of thermoset composites, depolymerisation and dissolution of thermosets and thermoplastics, closed loop recycling of glass, and the use of glass as a mechanical compatibiliser. 32 refs. 

Current methods of feedstock recovery are reviewed. Brief details are given of pyrolysis, hydrogenation, gasification, and chemolysis. Activities of some European companies are briefly discussed in the areas of recycling mixed plastics waste and closed-loop recycling. 

CLOSED-LOOP RECYCLING INSTEAD OF DOWN-GRADING... 

Closed-loop recycling. To further promote waste reduction and recycling, spent materials that are reclaimed and returned to the original process in an enclosed system of pipes and tanks are excluded from the definition of solid waste, provided that the following conditions are met ... 

A scrubber has a closed-loop recycle of caustic. The make-up caustic solution is added continuously on an ORP (oxidation-reduction potential) controller. The caustic concentration will typically be 20 wt% and thus the blow-down stream will contain approximately 15 wt% hypochlorite. Such a system will typically be provided with a large reservoir of caustic that is released on a once-through basis for containment of emergency relief streams or operated with a permanent excess of caustic, resulting in a hypochlorite concentration in the blow-down stream in the range of 6-12 wt%. 

Manufacturing process changes to simplify production technologies, reduce water and energy use, or introduce closed-loop recycling and... 

True Closed-Loop Recycling for Nylon, Environmental Building News, BuildingGreen.com, Vol. 8 (9), Brattleboro, VT, September 1999. 

Figure 21-11. Schematic diagram of the closed-loop recycling apparatns.

Closed loop recycling materials from class 1 and class 4 can be considered to be safe and in compliance with the legal requirements due to the absence of contamination or the high purification effect of the de- and re-polymerisation steps. The materials from class 2 and 3 should have been sorted to a polymer purity of about 99%, which means also that materials from non-food packaging should also be separated. However, for the special case of PET, the FDA also allows non-food PET as an input material as long as the polymer is in compliance with 21 CFR 177.1630. 

The initial equipment costs and operating costs for the more conventional processes are higher than for supercritical carbon dioxide. The higher equipment costs are due to the additional parts needed for environmental treatments (i.e., scrubbers, vapor incinerators, etc.) The consumables costs are lower for the supercritical fluid processes due to the closed-loop recycle design of the supercritical fluid system, elimination of water for rinsing and the reduced electricity costs associated with not having to dry the parts. 

Closed-loop recycling chromatography (reviewed by Dingenen and Kinkel 422)) may be necessary for separations of compt)unds with low enantioselectivity. 

Structural tile construction is commonly used in these units. The wall of the unit is thus a concrete wall with tile faces. The tile has traditionally been set with Portland cement mortar but modern bleach plant operations with closed loop recycling of chemicals has resulted in the increased use of resin mortars with their broader chemical resistance. 

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