PROCESS CONTROL FOR SIMUTANEOUS VITRIFICATION OF TWO MIXED WASTE STREAMS IN THE TRANSPORTABLE VITRIFICATION SYSTEM (TVS)

摘要

Two highly variable mixed (radioactive and hazardous) waste sludges were simultaneously vitrified in an EnVitCo Transportable Vitrification System (TVS) deployed at the Oak Ridge Reservation (ORR). The TVS was the result of a cooperative effort between the Westinghouse Savannah River Company (WSRC) and EnVitCo to design and build a transportable melter capable of vitrifying a variety of mixed low level wastes. The two waste streams for the demonstration were the dried B&C Pond sludges at the K-25 site and waste water sludge produced in the Central Neutralization Facility (CNF) from treatment of incinerator blowdown. Large variations occurred in the sodium, calcium, silicon, phosphorus, fluorine and iron content of the co-blended waste sludges: these elements have a significant effect on the processability and performance of the final glass product. The waste sludges were highly reduced due to organics added during processing (Betz 1138), coal-pile runoff (coal and sulfides), and other organics, including wood chips. A batch-by-batch process control model was developed to control glass viscosity, liquidus, and REDuction/OXidation (REDOX), assuming that the melter behaved as a Continuously Stirred Tank Reactor (CSTR).