Recycled utilization

M. Specht, A. Bandi, K Schaber, T. Weimer in CO2 Fixation Efficient Utilization of Energy, Y. Tamaura, K. Okazaki, M. Tsuji, S. Hirai (Eds.), Tokyo Institute of Technology, Research Center for Carbon Recycling Utilization, Tokyo, Japan (1993) 165... 

Considering the amount of total consumed uranium ( 7 t natural uranium for each ton enriched to 3.3% in U), the utilization of natural uranium is much less if plutonium is recycled, utilization increases to the overall figures given in Figure 19.9. 

Rao K. Value through recycling utilization of rejuvenated thermoplastic polymers for automotive applications. Annual recycling conference proceedings,99 1999. p. 457. 

In all commercial fuel cells, provision must be made for residual fuel effluent recovery. Fuel utilization is not 100% due to concentration polarization limitation on performance discussed in Chapters 3 and 4, so that unused fuel in the anode exhaust stream is always present and must be actively recycled, utilized, or converted prior to exhaust to the environment. Potential effluent management schemes include the use of recycling pumps, condensers (for Uquid fuel), secondary burners, catalytic converters, or dead-end anode designs. 

Clearly, the time chart shown in Fig. 4.14 indicates that individual items of equipment have a poor utilization i.e., they are in use for only a small fraction of the batch cycle time. To improve the equipment utilization, overlap batches as shown in the time-event chart in Fig. 4.15. Here, more than one batch, at difierent processing stages, resides in the process at any given time. Clearly, it is not possible to recycle directly from the separators to the reactor, since the reactor is fed at a time different from that at which the separation is carried out. A storage tank is needed to hold the recycle material. This material is then used to provide part of the feed for the next batch. The final flowsheet for batch operation is shown in Fig. 4.16. Equipment utilization might be improved further by various methods which are considered in Chap. 8 when economic tradeoffs are discussed. 

However, the concentration of impurity in the recycle is varied as shown in Fig. 8.5, so each component cost shows a family of curves when plotted against reactor conversion. Reactor cost (capital only) increases as before with increasing conversion (see Fig. 8.5a). Separation and recycle costs decrease as before (see Fig. 8.56). Figure 8.5c shows the cost of the heat exchanger network and utilities to again decrease with increasing conversion. In Fig. 8.5d, the purge... 

Commercially, fluorosulfuric acid is made by processes utilizing the product as a solvent. Solutions of HF and SO in fluorosulfuric acid are mixed in stoichiometric quantities, or SO and HF are separately introduced into a stream of fluorosulfuric acid to produce essentially pure HSO F. Some of the product is then recycled (50,51). 

The majority of thermal polymerizations are carried out as a batch process, which requires a heat-up and a cool down stage. Typical conditions are 250—300°C for 0.5—4 h in an oxygen-free atmosphere (typically nitrogen) at approximately 1.4 MPa (200 psi). A continuous thermal polymerization has been reported which utilizes a tubular flow reactor having three temperature zones and recycle capabiHty (62). The advantages of this process are reduced residence time, increased production, and improved molecular weight control. Molecular weight may be controlled with temperature, residence time, feed composition, and polymerizate recycle. 

For fine pulverization, both dry and wet processes are utilized, but increasingly the dry process is more popular because wet grinding ultimately requires drying and is much more energy intensive. A sensitive fan swirls the dust sizes into the air separator and permits coarse particles to recycle to the grinding mill or be rejected as tailings the fines are drawn into cyclones where the dust is collected. 

In the electrolysis of K2Mn04, one mole of KOH is coproduced for every mole of KMnO generated. This by-product potassium hydroxide must be recovered and utilized. For recycling, it also needs to be purified (130). Alternatively, the KOH can be converted into potassium carbonate by treatment with CO2 in the red-lye process (131). 

The recycling option is being utilized outside the United States. Whereas the technology of this option has been completely demonstrated ia the United States, the economics have not been favorable. Moreover, concerns have been raised as to the diversion of the plutonium to weapons use. Thus, the throwaway option is the only one ia use ia the United States as of this writing. 

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