Solid wastes vitrification

Waste treatment processes. See also Hazardous waste management Radioactive waste management Solid waste management for radioactive waste, 25 853-854 titanium-related, 25 64-65 Waste vitrification process, 12 616 Wastewater, 9 443. See also Effluent treatment... 

Vitrification A treatment technology for contaminated soils, sediments, and solid wastes that involves melting them to incinerate organic contaminants and encapsulate arsenic and other inorganic species in the resulting melts (compare with in situ vitrification). 

In Figure 2 the flow chart of classic fuel burning incinerator combined with plasma vitrification system of all solid residues is presented. The system is self-supplied in the electric power and it employs only single plasma furnace for vitrification of solids. This way every classic waste incineration plant can be converted to zero waste emission system. The excess of energy in the form of electricity or steam can be sold. 

Electro-Pyrolysis, Inc. (EPI) has developed the direct current (DC) graphite arc furnace vitrification technology for the ex situ treatment of wastes. The arc furnace can be operated as an oxidation or reduction process. The vendor states that DC arc melter treatment produces a leach-resistant solid and reduces the volume of wastes that require disposal. 

Vitrification is a high temperature process of immobilizing, and chemically incorporating, radioactive and other hazardous wastes. The procedure uses high temperatures (typically between 1100 and 1600 °C). At these temperatures, waste material is transformed into an amorphous liquid. On cooling, the vitrification produces an amorphous, glass-like solid that permanently captures the waste. Extremely hazardous wastes and radioactive wastes can be immobilized by this method. 

The use of nuclear power as energy source is determined by the safe handling and deposition of the nuclear waste. High active waste solutions must be transformed into stable solid form which is suitable for final disposal. The separation of the actinides from the waste before its solidification (e.g. vitrification) is advantageous (or may be even necessary) from two points of view ... 

An alternative calcination process derived from the Idaho Waste Calcining Facility to be employed in connection with a vitrification unit has been developed to take advantage of the excellent heat transfer and solid mixing properties of fluidized beds. Silica is used as bed particles and is continuously fed into the bed at the rate needed in the final glass. 

Thermal plasmas can be effective in compaction and destraction of liquid and solid hazardous wastes (Watanabe, 2003), including treatment of radioactive wastes by plasma incineration and vitrification for final disposal (Tzeng et al., 1998), plasma compaction... 

The Windscale Vitrification Plant vitrifies high level (highly active) liquid waste arising from reprocessing operations at Sellafield. The plant operates two identical vitrification lines with a current combined throughput of 350 product containers per year. A third line is currently under construction and will commence operation in the year 2000. The key safety function of the plant is to convert mobile material into a solid immobile form which can be more easily managed, stored, and transported. 

The Vitrification Plant processes HAL into a solid vitrified waste form that is then stored in a dedicated storage facility. The vitrification plant process is described below, considering each of the main cells in the plant in sequential process order ... 

HLW generally refers to materials requiring permanent isolation from the environment. It frequently arises as a by-product of nuclear power generation (reprocessing streams or spent fuel) or from the isolation of fissile radionuclides from irradiated materials to be used in nuclear weapons production. When nuclear fuel from reactor operations (civilian or defense) is chemically processed, the radioactive wastes include highly concentrated liquid solutions of nuclear fission products. Typically, these waste streams are solidified either in a glass (vitrification) or in another matrix. Both the liquid solutions and the vitrified solids are considered HLW. If the nuclear fuel is not processed, it too, is considered as HLW and must be dispositioned. The path most often proposed is direct, deep geologic isolation. 

Vitrification produces a stable solid that has the HLW incorporated its structure. A year s waste from a 1000 MWe reactor is contained in 51 of such glass, or about 12 canisters 1.3 m high and 0.4 m in diameter. These can be readily transported and stored, with appropriate shielding. 

Because of the anion complexation observed in the solid state, it was proposed that cyclo[8]pyrrole could function as an anion extractant, specifically for sulfate. Sulfate receptors that can act as extractants of this ion are highly desirable because sulfate is a problematic species in the vitrification process that is proposed for the disposal of certain radioactive wastes. The original reported short-chained forms of cyclo[8]pyrrole presented solubility issues, but a newer derivative, octamethyl-octaundecylcyclo[8]pyrrole, 2b, originally developed as a precursor for liquid crystals, proved to be amenable to extraction studies. It was found that 2b was able to selectively extract sulfate in the presence of high levels of nitrate. This cyclo[8]pyrrole was thus able to overcome the so-called Hofmeister bias or the inherent propensity for nitrate to partition before sulfate. While the kinetics are slow—reducing utility in the context of near-term applications—this is the first example where this level of selectivity is seen in a sulfate versus nitrate extraction experiment. ... 

Vitrification is one technique for storing nuclear waste. The liquid waste is heated to a high temperature and mixed with substance that forms a glassy solid when cooled. This prevents problems associated with storing liquids in tanks that may leak. 

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