Cold cap subsidence for in situ vitrification and electrodes therefor

Patent · 01 January 1992

OSTI ID:868214

Buelt, James L ^[1]; Carter, John G ^[1]; Eschbach, Eugene A ^[1]; FitzPatrick, Vincent F ^[1]; Koehmstedt, Paul L ^[1]; Morgan, William C ^[1]; Oma, Kenton H ^[1]; Timmerman, Craig L ^[1]

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1. Richland, WA

An electrode for use in in situ vitrification of soil comprises a molybdenum rod received within a conductive sleeve or collar formed of graphite. Electrodes of this type are placed on either side of a region containing buried waste material and an electric current is passed therebetween for vitrifying the soil between the electrodes. The graphite collar enhances the thermal conductivity of the electrode, bringing heat to the surface, and preventing the formation of a cold cap of material above the ground surface. The annulus between the molybdenum rod electrode and the graphite collar is filled with a conductive ceramic powder of a type that sinters upon the molybdenum rod, protecting the same from oxidation as the graphite material is consumed, or a metal powder which liquifies at operating temperatures. The molybdenum rod in the former case may be coated with an oxidation protectant, e.g. of molybdenum disilicide. As insulative blanket is suitably placed on the surface of the soil during processing to promote subsidence by allowing off-gassing and reducing surface heat loss. In other embodiments, connection to vitrification electrodes is provided below ground level to avoid loss of connection due to electrodes deterioration, or a sacrificial electrode may be employed when operation is started. Outboard electrodes can be utilized to square up the vitrified area. Further, the center of the molybdenum rod can be made hollow and filled with a powdered metal, such as copper, which liquifies at operating temperatures. In one embodiment, the molybdenum rod and the graphite collar are physically joined at the bottom.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA
• DOE Contract Number: AC06-76RL01830
• Assignee: Battelle Memorial Institute (Richland, WA)
• Patent Number(s): US 5100259
• OSTI ID: 868214
• Country of Publication: United States
• Language: English

Related Subjects

/405/166/219/
allowing
annulus
avoid
below
below ground
blanket
bottom
bringing
buried
buried waste
cap
center
ceramic
ceramic powder
coated
cold
cold cap
collar
collar formed
comprises
conductive
conductive ceramic
conductive sleeve
conductivity
connection
consumed
containing
copper
current
deterioration
disilicide
due
electric
electric current
electrode
electrodes
embodiment
embodiments
employed
enhances
filled
formation
formed
former
graphite
graphite collar
ground
ground level
ground surface
heat
heat loss
hollow
insulative
joined
level
liquifies
loss
material
metal
metal powder
molybdenum
molybdenum disilicide
molybdenum rod
off-gassing
oil comprises
operating
operating temperature
operating temperatures
operation
outboard
oxidation
passed
physically
physically joined
placed
powder
powdered
powdered metal
preventing
processing
promote
protectant
protecting
provided
received
reducing
region
region containing
rod
rod electrode
rod received
sacrificial
sinters
situ
situ vitrification
sleeve
soil
square
started
subsidence
suitably
surface
surface heat
temperatures
therebetween
thermal
thermal conductivity
type
utilized
vitrification
vitrified
vitrifying
waste
waste material