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