Recycled products

Where possible, introducing extraneous materials into the process should be avoided, and a material already present in the process should be used. Figure 4.6h illustrates use of the product as the heat carrier. This simplifies the recycle structure of the flowsheet and removes the need for one of the separators (see Fig. 4.66). Use of the product as a heat carrier is obviously restricted to situations where the product does not undergo secondary reactions to unwanted byproducts. Note that the unconverted feed which is recycled also acts as a heat carrier itself. Thus, rather than relying on recycled product to limit the temperature rise (or fall), simply opt for a low conversion, a high recycle of feed, and a resulting small temperature change. 

Methyl Chloride. Most of the HCl consumed in the manufacture of methyl chloride [74-87-3] from methanol (qv) is a recycled product. The further reaction of methyl chloride with chlorine to produce higher chlorinated methanes generates significant amounts of HCl which are fed back into methyl chloride production. Another source of recycled HCl is siUcone production based on methyl chloride. 

It is not tme either that vinyl is the problem in municipal recycling because it contaminates other resins. Contamination occurs whether or not vinyl is present. Other resins are just as much a contamination problem as vinyl. Except for commingled plastics apphcations, different plastic materials caimot be mixed successfiJly in most recycled products apphcations. This is why it is cmcial to separate efficientiy one plastic from another. Because of the chlorine that is present in it, vinyl lends itself very weU to automated sorting technology. 

The Sbddeutsche Kalkstickstoffwerke process at Trostberg uses powdered calcium carbide along with recycle product and calcium fluoride ia a rotary kiln at 1000—1100°C. The capacity of a unit is 25 t fixed nitrogen per day. The product passes to a rotary cooler and is granular (21). 

Any type of sohds conveyor may be suitable for recycle mixing however, the most universally applicable is the double-shaft pug-miU-type paddle mixer. This conveyor or mixer should be insulated to prevent excessive heat losses from the hot, dry recycle product. To ensure uniformity in the recycle operation, a surge storage reserve of recycle sohds should be installed for startup purposes and in the event of interruption of product discharge from the cyhnder. In recycle operations, 50 to 60 percent product recirculation is found economical in many instances. 

The reaction section consists of the high pressure reactors filled with catalyst, and means to take away or dissipate the high heat of reaction (300-500 Btu/lb of olefin polymerized). In the tubular reactors, the catalyst is inside a multiplicity of tubes which are cooled by a steam-water condensate jacket. Thus, the heat of reaction is utilized to generate high pressure steam. In the chamber process, the catalyst is held in several beds in a drum-type reactor with feed or recycled product introduced as a quench between the individual beds. 

The fire was more serious than it would normally have been because the inventory in the plant, about 70 tons, was about twice the usual amount. Some of the overheads from a reactor were collected in a slops drum and recycled. The inventory in the drum was usually small. At about 9 a.m. on the day of the fire, the recycle pump failed. As a result, the level in the drum rose, and the level in the reactor fell. The operator noticed the fall in the reactor level (but not the rise in the drum level) and recycled product to maintain the level. At 8 p.m. the supervisor noticed that the high-level alarm on the slops drum was lit he found that the recycle pump had failed, and he changed over to the spare it leaked 25 minutes later. Section 3.3.1 describes another occasion when operators failed to notice unusual readings for 11 hours. 

Procurement policies regarding goveriuiient purcliase of recycled products, reusable products, and products designed to be recycled... 

Total feed from caustic scrubber Hydrogen addition First-stage fresh feed First-stage recycle Second-stage fresh feed Second-stage recycle Product gas... 

DuPont has recently announced plans to build a demonstration plant in Maitland, Ontario, to show that the quality of the recycled product is equivalent to the virgin material (64). BASF converts post-consumer carpet into caprolactam in Ontario. Rhodia has several European plants for depolymerising nylon 6. 

Davos, 22nd-26th March 1993, paper 23/4. 8(13) RECYCLING PRODUCT, EEEDSTOCK OR ENERGY - A FUTURE VIEW Dennison M T... 

Klingensmith, B., Recycling, production and use of reprocessed rubbers, Rubber World, 203, 16, 1991. Drozdovskii, V.F., Production of comminuted vulcanizates, Prog. Rubber Plast. TechnoL, 14, 116, 1998. 

The first stage of the process is a hydroformylation (oxo) reaction from which the main product is n-butyraldehyde. The feeds to this reactor are synthesis gas (CO/H2 mixture) and propylene in the molar ratio 2 1, and the recycled products of isobutyraldehyde cracking. The reactor operates at 130°C and 350 bar, using cobalt carbonyl as catalyst in solution. The main reaction products are n- and isobutyraldehyde in the ratio of 4 1, the former being the required product for subsequent conversion to 2-ethylhexanol. In addition, 3 per cent of the propylene feed is converted to propane whilst some does not react. 

The presence of the enamino moiety in 2-amino-4H-pyrans accoimts for their ability to undergo recyclizations into various pyridones, 1,4-dihy-dropyridines, and 2H-pyrones-2. To some extent, properties of 2-amino-4H-pyrans in reactions with nucleophiles can be compared to those of pyrillium salts (68T5059,80T697) because they also tend to form recyclized products. Reactions proceed in the presence of bases or acids. Naphthopyrans 133 form 2-alkoxypyridines 261 on the action of sodium alcoholates or ethanolic NaOH (79M115) (Scheme 101). 

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