Recycling considerations

Batch versus continuous Flowsheet input-output structure Crystallizer and recycle considerations Separation systems specification Product drying Energy systems... 

A survey is made of methods for the recycling of PVC and mixed waste containing PVC, including incineration with energy recovery, pyrolysis and chemical recycling. Consideration is also given to the flammability of PVC and the toxicity of its combustion products. 82 refs. 

P. Patil, G.L. Henriksen, D.R. Vissers, and C. Christianson, "Shipping, Use and Disposal/Recycle Considerations for the Sodium/Beta Batteries in EV Applications," presented at the DOE/EPRI Beta (Sodium/Sulfiir) Battery Workshop VIII, Chester, England, June 1990. 

Textiles can be mechanically or chemically broken down to the fibre for recycling. Additionally, other forms of post-consumer waste such as PET bottles may be recycled into fibre for apparel. For all forms of recycling, considerations include the blend of fibres or polymers, the length of these fibres, to what degree the textile or product can be broken down and the cleanliness or degree of impurities of the feedstock to be recycled (Gulich, 2006b). 

Level of cleanliness required Type and amount of organic contaminant Type, size, composition and amount of particulate contaminant Co-solvent requirements Type of parts to be cleaned (e.g., size, complexity, porosity, loading density, pressure sensitivity) Production capacity Breadth of application Temperature, pressure, separator efficiency, cycle time Temperature, pressure, co-solvents Flow rate, agitation, filtration Type, quantity, emission control and recycle considerations Dimensions, fixturing and flow pattern within cleaning vessel process control strategy Parts per cycle and cycles per work period Number of different processes that must be performed by the system... 

For example, post-stabilizing allows to increase the long-term heat stabilization of a PP/EPDM bumper recyclate considerably, so that common requirements for these applications are met easily. Fig. 3.22 [533]. 

This type of plant has been considered by Papadourakis et al. (1987), and Luyben (1993). Though conceptually simple, the use of recycle considerably complicates steady-state and transient operations. 

The recycling of material is an essential feature of most chemical processes. Therefore, it is necessary to consider the main factors which dictate the recycle structure of a process. We shall start by considering the function of process recycles and restrict consideration to continuous processes. Later the scope will be extended to include batch processes. 

Additional separation and recycling. Once the possibilities for recycling streams directly, feed purification, and eliminating the use of extraneous materials for separation that cannot be recycled efiiciently have been exhausted, attention is turned to the fourth option, the degree of material recovery from the waste streams that are left. One very important point which should not be forgotten is that once the waste stream is rejected, any valuable material turns into a liability as an effluent material. The level of recovery in such situations needs careful consideration. It may be economical to carry out additional separation of the valuable material with a view to recycling that additional recovered material, particularly when the cost of downstream effluent treatment is taken into consideration. 

Points to Consider for the Use of Recycled Plastics in Food Packaging Chemistry Considerations, U.S. Food and Dmg Administration, Center for Food Safety and Apphed Nutrition, PubUcation HFS-245, Washington, D.C., April 1992. 

High purity acetaldehyde is desirable for oxidation. The aldehyde is diluted with solvent to moderate oxidation and to permit safer operation. In the hquid take-off process, acetaldehyde is maintained at 30—40 wt % and when a vapor product is taken, no more than 6 wt % aldehyde is in the reactor solvent. A considerable recycle stream is returned to the oxidation reactor to increase selectivity. Recycle air, chiefly nitrogen, is added to the air introducted to the reactor at 4000—4500 times the reactor volume per hour. The customary catalyst is a mixture of three parts copper acetate to one part cobalt acetate by weight. Either salt alone is less effective than the mixture. Copper acetate may be as high as 2 wt % in the reaction solvent, but cobalt acetate ought not rise above 0.5 wt %. The reaction is carried out at 45—60°C under 100—300 kPa (15—44 psi). The reaction solvent is far above the boiling point of acetaldehyde, but the reaction is so fast that Httle escapes unoxidized. This temperature helps oxygen absorption, reduces acetaldehyde losses, and inhibits anhydride hydrolysis. 

The ammonia values can be recycled or sold for fertilizer use. The most important consideration ia this process is the efficient elimination of the phosphoms from the product, because as Htfle as 0.01% P2 5 electrolyte causes a 1—1.5% reduction ia current efficiency for aluminum production (28). 

The selection of a particular type of reduction depends on technical feasibiUty and the economics of the process as well as on physicochemical considerations. In particular, the reducing agent should be inexpensive relative to the value of the metal to be reduced. The product of the reaction, RX, should be easily separated from the metal, easily contained, and safely recycled or disposed of. Furthermore, the physical conditions for the reaction should be such that a suitable reactor can be designed and operated economically. 

Isopropylnaphthalenes can be prepared readily by the catalytic alkylation of naphthalene with propjiene. 2-lsopropylnaphthalene [2027-17-0] is an important intermediate used in the manufacture of 2-naphthol (see Naphthalenederivatives). The alkylation of naphthalene with propjiene, preferably in an inert solvent at 40—100°C with an aluminum chloride, hydrogen fluoride, or boron trifluoride—phosphoric acid catalyst, gives 90—95% wt % 2-isopropylnaphthalene however, a considerable amount of polyalkylate also is produced. Preferably, the propylation of naphthalene is carried out in the vapor phase in a continuous manner, over a phosphoric acid on kieselguhr catalyst under pressure at ca 220—250°C. The alkylate, which is low in di- and polyisopropylnaphthalenes, then is isomerized by recycling over the same catalyst at 240°C or by using aluminum chloride catalyst at 80°C. After distillation, a product containing >90 wt % 2-isopropylnaphthalene is obtained (47). 

As the recycled fuel composition approaches steady state after approximately four cycles (1), the heat and radiation associated with and Pu require more elaborate conversion and fuel fabrication facihties than are needed for virgin fuel. The storage, solidification, packaging, shipping, and disposal considerations associated with wastes that result from this approach are primarily concerned with the relatively short-Hved fission products. The transuranic... 

Based on the evidence that acceptable recycled petroleum products can be produced, there is a considerable legislative record encouraging the recycling of used oil. Starting with the Resource Conservation and Recovery Act in 1976 (20), used oil was held apart from the normal hazardous waste system because the oil was viewed as a valuable commodity. This was followed by the Used Oil Recycling Act in 1980 (33), which removed any federal requirement that lubricants containing re-refined base oil carry special labeling. 

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