Residue recycling

Primary waste generation is small because of the high density nature of the fused salt operations. Nearly all primary waste residues show excellent potential for recycle. (The present main processing sequence for plutonium does not include significant reagent and residue recycle). 

Process Schematic. A schematic showing our main production sequence and our present plutonium residue recycle streams is seen in Figure 10. The oval-shaped steps, representing the recycle streams, are as follows ... 

Figure 10. Main production sequence plus present Pu residue recycle.

Figure 12. Main production sequence, present Pu residue recycle, proposed Pu residue recycle, and proposed reagent recycle.

Ethylene is to be converted by catalytic air oxidation to ethylene oxide. The air and ethylene are mixed in the ratio 10 1 by volume. This mixture is combined with a recycle stream and the two streams are fed to the reactor. Of the ethylene entering the reactor, 40% is converted to ethylene oxide, 20% is converted to carbon dioxide and water, and the rest does not react. The exit gases from the reactor are treated to remove substantially all of the ethylene oxide and water, and the residue recycled. Purging of the recycle is required to avoid accumulation of carbon dioxide and hence maintain a constant feed to the reactor. Calculate the ratio of purge to recycle if not more than 8% of the ethylene fed is lost in the purge. What will be the composition of the corresponding reactor feed gas ... 

What is the disposition of final treatment residuals Recycle Hazardous waste landfill Nonhazardous waste landfill Other Some secondary wastes, even after treatment, may be considered hazardous and may need to be disposed of accordingly. Some types of secondary wastes may be released as is for reuse or recycling. 

The objective of this stage is to remove the traces of heavy metals contained in the concentrated raffinate, so that the ammonium salts comply with commercial specifications. The purification process consists of the precipitation of metallic sulphides by adding sodium sulphide to the concentrated raffinate. The generated suspension is filtered, leaving a mixture of ammonium sulphate and chloride concentrated solution, that is pumped to the fertilizer plant (fertlizer operations). The solid residue recycled to the lead smelter. The operating conditions are ... 

IWT test facility /shaft gasifier X X Tube filter and wet tar washing Staged waste water treatment, evaporation, vapour residue recycling Recycling in the process, discharge of weiste water into the sewer system possible... 

Atmospheric Leach and Precipitation Processes. Aluminum is completely precipitated at the pH used for ferrous iron oxidation. The precipitated aluminum reports to the residue recycle stream and is releached in the Induced Jarosite Precipitation stage. There is therefore the risk of a recirculating load building up in the circuit between the Induced Jarosite Precipitation and Secondary Neutralization circuits. However, the pH of the intervening Primary Neutralization step is sufficiently high to precipitate excess aluminum and provide a safe bleed from the process. 

X. Ruan, G. He, B. Li, J. Xiao, and Y. Dai, Cleaner recovery of tetrafluoroethylene by coupling residue-recycled polyimide membrane unit to distillation. Separation and Purification Technology, 124, 89-98, 2014. 

Figure 8. Single Step Hydrocracking. Residue Recycle at 2nd Reactor.

The techno-economic analysis of two stage membrane processes for post-combusion CO2 capture revealed that CO2 capture by membranes appears to be feasible. Nevertheless, the CO2 product stream contains at least 1 vol.% O2, thus violating strict purity requirements, e.g. for enhanced oil recovery. Membrane costs substantially affect the optimal operation mode of the capture process. Residual recycling is particularly attractive to enhance overall CO2 recovery. Since the application of residual recycling leads to a flat minimum of the avoidance costs, capture levels between 80% and 95% seem to be most attractive. 

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