Apparatus for the decomposition of hazardous materials and the like

A method and apparatus for the destruction of PCBs and other hazardous material utilizes a gas-tight chamber (18) which includes a high current DC arc (72). The chamber (18) is adapted to receive the PCBs or other hazardous material and includes a sump (20) which contains a molten bath (22). Inlet means (24, 26, 28) are provided for introducing the hazardous material into the chamber (18) and into contact with the molten bath (22) for initial decomposition into a molten product and a gaseous product. Electrode means (66, 68) are provided for maintaining the DC arc (72) at a current level sufficient to promote decomposition of the PCBs or other hazardous material. The gaseous product is passed in the proximity of the arc (72) for producing a decomposed gaseous product which is relatively harmless. The system is capable of decomposition of solid, liquid and gaseous PCBs, as well as other hazardous material.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a method and apparatus for the 
decomposition of hazardous materials, such as polychlorobiphenyls (PCBs) 
and the like, and, more particularly, to such a method and apparatus for 
the pyrolysis of PCBs and other such hazardous materials utilizing a D.C. 
arc in a sealed electric arc furnace. 
DESCRIPTION OF THE PRIOR ART 
Polychlorobiphenyl materials (PCBs) have been used extensively in the past 
in electrical equipment such as transformers and capacitors, due in a 
large part to their flame retardant characteristic, high temperature 
stability, inertness to biodegradation and excellent dielectric 
properties. Other uses in mining equipment, hydraulic systems and heat 
transfer systems were prompted by these same properties. 
In the nineteen sixties it was discovered that PCBs were highly toxic and 
the environmental impact of PCB contamination received a great deal of 
coverage in the public press. The fact that PCBs were found to be 
carcinogenic in mice and are extremely stable has resulted in the 
enactment of legislation severely restricting the manufacturing, 
processing and sale of PCBs. The storage and disposal of existing PCBs and 
materials containing PCBs has also been the subject of legislation, as 
well as regulation by governmental agencies, such as the Environmental 
Protection Agency. The exceptional chemical stability which makes PCBs 
useful as a dielectric fluid and heat transfer agent also makes it 
extremely difficult to destroy. 
Four basic techniques have been previously developed for PCB disposal: 
landfill; chemical destruction; biological destruction; and 
incineration/pyroylsis. 
The simplest and lowest cost technique used for disposal of PCBs has been 
by landfill. However, at the present time there is only a relatively small 
number of landfill sites which have obtained the requisite permits from 
the Environmental Protection Agency and other government agencies for 
receiving and disposing of PCBs. In the present era of increasing public 
awareness and with the existing regulatory structure, it is unlikely that 
a significant number of new landfill sites will be approved for disposal 
of PCBs. In addition, the existing governmental regulations only permit 
the disposal of solid materials contaminated by PCBs at landfill sites 
(liquid PCBs must be incinerated), thereby necessitating the prior 
draining, flushing and storage of all liquid PCBs. Thus, it is clear that 
the disposal of PCBs utilizing landfill sites is not a viable final 
solution to the PCB disposal problem. 
Various chemical treatment processes have reportedly been successfully used 
for the destruction of small quantities of PCBs in the laboratory. One 
such technique involves the treatment of PCBs with alkaline 2-propanol 
solution followed by exposing the resulting material to ultraviolet light 
for a predetermined period of time. Another such chemical treatment 
technique involves the stepwise removal of electrons from the aromatic 
ring system of the PCBs, followed by hydrolysis, solvolysis, oxidative 
coupling and dimerization utilizing high anodic potentials in 
acetonitrile. 
While the above-described chemical treatment process, as well as other 
chemical treatment processes, have achieved some success in the 
decomposition of PCBs, the techniques have only been employed in 
connection with very small quantities of PCBs. These chemical treatment 
processes would be cumbersome and extremely expensive to employ in 
connection with the decomposition of large quantities of PCBs. In 
addition, some of the chemical treatment processes have resulted in the 
generation of hazardous by-products, which require additional special 
handling and destruction. 
Although PCBs are generally thought to be extremely resistant to biological 
or enzyme attack, recent studies have shown that some PCBs are degradable 
by certain strains of bacteria and soil fungus. One such technique 
involves the use of acromasacter (two species) pseudomonas sp, 
acinetrobacter sp strain y42+33, and acinetobacter sp strain P6 to 
oxidatively degrade PCBs to chlorobenzoic acids. A second technique as 
described in U.S. Pat. No. 3,779,866 employs strains of caldosporium 
cladosporicides, candidelipolytice, nocardia globerola, nocardia rubra 
and/or saccharomyces cerevisiae to totally destroy PCBs. 
Again, while the above-described and other biological techniques have 
achieved some success in the destruction of PCBs in limited quantities, 
none of these biological techniques have offered a solution to the 
disposal of large quantities of PCBs in an environmentally sound manner at 
a reasonable cost. 
In regard to incineration of PCBs, it has been found that PCBs have high 
thermal stability and generally require combustion temperatures on the 
order of 1600.degree. C. for total destruction. Although numerous prior 
art attempts have been made to develop a method or system for the 
incineration of PCBs utilizing different variations of conventional 
combustion techniques, the prior art methods and processes for the most 
part have been unsuccessul primarily due to the extreme difficulty 
involved in maintaining the required 1600.degree. C. temperature. The 
failure to maintain the requisite temperature generally results in an 
incomplete destruction of the PCBs and may result in the generation of 
even more toxic by-product materials, such as hexachlorobenzene or 
polychlorinated dibenzofurans. In addition, the prior art 
incineration/pyroloysis methods were primarily used for the destruction of 
liquid PCBs due to difficulties in employing such methods in connection 
with solids. Furthermore, the prior art techniques resulted in the 
generation of large volumes of gas which had to be collected and scrubbed 
to remove various impurities therefrom. 
The present invention was developed to overcome various problems associated 
with a number of prior art destruction processes. More specifically, the 
present invention comprises a method and apparatus for the destruction of 
PCBs and other hazardous materials utilizing a totally sealed system, 
which includes a high current DC arc for maintaining a temperature 
considerably in excess of 1600.degree. C. and for providing bond-breaking 
ultraviolet and other radiation. The use of the DC arc assures that the 
original PCBs are decomposed into relatively harmless gaseous components 
and that no dangerous intermediate chemicals remain in the exhaust gas. 
The system of the present invention is capable of effective decomposition 
of both solid and liquid PCBs and, due to the lack of oxygen or other 
atmospheric gases present in the sealed system, the need for excessive 
containment and scrubbing equipment for the exhaust gases is effectively 
reduced. 
SUMMARY OF THE INVENTION 
Briefly stated, the present invention comprises a method and apparatus for 
the decomposition of hazardous material utilizing an electrical direct 
current (DC) arc. A gas-tight chamber is adapted to receive the hazardous 
material, the chamber including a sump which contains a molten bath. Inlet 
means are provided for introducing the hazardous material into the chamber 
and the molten bath for initial decomposition thereof into a product 
within the molten bath and a gaseous product which remains within the 
chamber. Electrode means are provided for maintaining a DC arc within the 
chamber, the arc having a current level sufficient to promote the 
decomposition of the hazardous material. An exhaust means is provided 
within the chamber proximate to the arc for the removal of gases from the 
chamber. Gases liberated into the chamber are passed in the proximity of 
the arc for undergoing decomposition prior to their removal through the 
exhaust means.

DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS 
Referring to FIG. 1, there is shown a schematic view of an apparatus or 
pyrolytic furnace indicated generally as 10, for the decomposition of 
liquid, solid or gaseous hazardous materials or any combination thereof, 
such as polychlorobiphenyls (PCBs), PCB contaminated liquids and solids 
and the like, into innocuous gases by pyrolysis employing a D.C. arc. It 
has been found that by subjecting PCBs and PCB contaminated liquids and 
solids to a two-step process in which they are initially exposed to a high 
temperature (such as in a molten bath) to promote initial decomposition 
into a gaseous product and then exposing the gaseous product to a high 
current, high temperature D.C. arc, the resulting gaseous product produced 
comprises CO, CO.sub.2, H.sub.2, CH.sub.4 and HCl. 
The furnace 10 comprises, in this embodiment, a generally cylindrical 
housing 12 having an outer containment shell 14, which may be comprised of 
steel or any other similar electrically conductive structural material, 
and an inner refractory lining 16, which may be comprised of any suitable 
known electrically conductive furnace lining material, for example, 
graphite. Because of the high temperatures and pressures involved in the 
decomposition process conducted within the furnace 10, the outer shell 14 
and/or the inner lining 16 must be capable of withstanding an interior 
pressure of five atmosphere and may be cooled in any conventional manner, 
for example, by circulating cooling fluid (such as water) through fluid 
passages (not shown) which may be embedded within or adjacent to the outer 
shell 14 and/or the inner lining 16. 
Due to the hazardous nature of the PCBs and other materials which are to be 
decomposed within the furnace 10, it is important that the furnace 10 be 
carefully constructed to maintain a completely gas-tight chamber 18 within 
which the decomposition takes place. Suitable seals (not shown) are 
employed where required to maintain the chamber 18 in a gas-tight 
condition. In this manner, leakage of unreacted or partially decomposed 
toxic gases into the atmosphere can be avoided. In addition, in the 
gas-tight chamber, the presence of oxygen in the furnace 10 can be avoided 
to thereby provide a reducing environment which permits the use of 
unconventional lining material (such as graphite which would quickly 
deteriorate from burning in the presence of oxygen) for the furnace 10. 
The lower portion of the furnace 10 forms an annular sump 20 within the 
chamber 18. The sump 20 has maintained therein a molten bath 22 comprised 
of metals, salts or any other suitable material which, in its molten 
state, is a good electrical conductor. The molten bath 22 serves to 
promote the initial decomposition or volitization of the PCBs and other 
hazardous materials, which may be introduced into the furnace 10, into a 
gaseous product which is liberated into the chamber 18 above the molten 
bath 22. In addition, the molten bath 22 serves to melt or decompose any 
other organic or inorganic materials which may be introduced into the 
furnace and remain in the molten bath. Such organic or inorganic materials 
may include, for example, the metal, plastic or cellulose packaging 
materials which were employed to contain the PCBs. It is considered 
necessary to destroy such container materials since, due to their prior 
contact with the PCBs, they are also considered to be hazardous. 
As will hereinafter be described in more detail, the temperature of the 
molten bath 22 is maintained at a level commensurate with the volitization 
temperature of the particular hazardous material being decomposed. For 
example, when PCBs are being decomposed, the temperature level of the 
molten bath may be on the order of 1500.degree. C., which is lower than 
the temperature for complete destruction of PCBs in the prior art, but 
lower temperatures are possible in the present system due to the use of 
the arc which significantly aids the destruction process. 
The furnace 10 includes inlet means, shown generally as 24, for charging or 
introducing the hazardous material from the outside of the housing 12 into 
the chamber 18. The inlet means 24 comprises a plurality of individual 
charging ports positioned at various locations around the circumference of 
the housing 12. By positioning the charging ports around the circumference 
of the housing 12, the PCBs or other hazardous material may be immersed 
into different areas of the molten bath 22 (perhaps sequentially) to 
thereby prevent excessive localized cooling of the molten bath 22 which 
may occur if only a single charging port is employed. The charging ports 
must be capable of introducing PCBs or other hazardous material into the 
chamber 18 while maintaining a generally gas-tight system. In this manner, 
the furnace 10 has the capability of operating batch (one charge of 
hazardous material at a time) or operating continuously (continuous 
addition of hazardous material). 
In the present embodiment, two different types of charging ports 26 and 28 
are shown and will hereinafter be described in some detail. Furnace 10 may 
include one or more of each type of the charging ports 26 and 28 or may 
include one type of charging port or ports. Charging ports 26 and 28, 
which each comprise a two stage air-lock arrangement, are but two examples 
of the types of charging ports which may be employed for introducing 
hazardous material into the chamber 18. Therefoe, it should be appreciated 
that the present invention is not limited to the specific type or 
combination of charging ports disclosed but could employ any other 
suitable type or combination of inlet means which allows for introduction 
of hazardous material into the furnace 10 while effectively maintaining 
the chamber 18 in a gas-tight condition to prevent the escape of any toxic 
or otherwise hazardous gas. 
Charging port 26 is particularly suited for introducing, for example, 
capacitors designated 29 into the furnace 10. Capacitors 29 of the type 
shown may comprise ceramic, cellulose plastic metal and some form of 
generally sealed metalic outer container which enclose (sometimes under 
pressure) liquid PCBs as a dielectric element. Both the PCBs within the 
container and the container itself must be disposed of as hazardous 
materials. The charging port 26 comprises a sealed (gas-tight) generally 
tubular passage 30 having an entry port 32 on a first or outer end and an 
exit port 34 on the second or inner end. The sealed passage 30 further 
includes a closable partition means 36 positioned approximately halfway 
between the entry port 32 and the exit port 34 to divide the sealed 
passage into a first outer compartment 38 adjacent to the entry port 32 
and a second inner compartment 40 adjacent to the exit port 34. Each of 
the ports 32 and 34 and partition 36 are adapted to open and close 
independently of each other and to provide tight seals when closed, so 
that the charging port 26 has the capability of continuously charging or 
introducing material into the furnace 10 while continuing to maintain the 
gas-tight condition of the chamber 18. 
In the operation of the inlet device 26, the ports 32 and 34 and partition 
36 are initially closed as shown. The entry port 32 is then opened and 
capacitor 29, or other solid or liquid hazardous material to be decomposed 
or destroyed, is admitted or inserted into the first compartment 38 as 
shown. The entry port 32 is then closed and the first compartment 38 is 
evacuated (employing any known suitable means) to prevent the introduction 
of oxygen into the chamber 18. Thereafter, the partition 36 is opened and 
the capacitor 29 is passed from the first compartment 38 into the second 
compartment 40. In the embodiment shown on FIG. 1, the tubular passage 30 
slopes slightly downwardly so that the capacitor 29 may simply slide or 
roll downwardly from the first compartment 38 through the partition 36 to 
the second compartment 40. Alternatively, any other suitable means could 
be employed for moving the capacitor 29 from the first compartment 38 to 
the second compartment 40, such as a push rod (not shown) or a conveyor 
belt (not shown). 
Once the capacitor 29 is positioned within the second compartment 40, the 
partition 36 is again closed and the first compartment 38 is evacuated to 
prevent the escape (to the atmosphere) of any toxic gas when the entry 
port 32 is opened again. The exit port 34 is then opened and the capacitor 
29 passes from the second compartment 40 along the downwardly sloping 
passage 30 and into the molten bath 22. As previously mentioned, any other 
suitable means may be employed for moving the capacitor 29 from the second 
compartment 40 into the molten bath 22. 
While in some cases it is desirable to have entire capacitors inserted 
directly into the molten bath 22 as described above, in other cases this 
is not an acceptable procedure. Because of the size and construction of 
some capacitors, and particularly large pressure sealed capacitors, the 
immersion of the entire capacitor directly into the molten bath 22 would 
result in a build-up in pressure within the capacitor and eventually a 
violent or uncontrolled explosion which may result in potential damage to 
the furnace. In order to alleviate the potential explosion hazard, the 
second compartment 40 may include suitable means 42, for example the 
multi-pronged "iron maiden" shown in FIG. 1, for puncturing and/or 
crushing the capacitor 29 in order to prevent the formation of excessive 
pressure. In addition, by puncturing or crushing the capacitor 29 in this 
manner, the liquid PCBs within the capacitor 29 are permitted to drain 
from the capacitor container. 
The lower end of the second compartment 40 includes an opening into a 
conduit means or drain pipe 44 which communicates with the interior of the 
chamber 18 as shown. The drain pipe 44 receives liquid PCBs from the 
punctured or crushed capacitor 29 and allows liquid PCBs to flow into the 
molten bath 22. The liquid PCBs may be preheated utilizing waste heat from 
the furnace 10 (not shown) prior to their entering the molten bath 22. A 
suitable valve means 46, which may be provided by any suitable known 
control valve, may be installed within the drain pipe 44 in order to 
restrict and control the flow of liquid PCBs into the molten bath 22. In 
addition, the liquid PCBs may be pressurized, atomized and sprayed (not 
shown) against the surface of the molten bath 22 to provide more intimate 
contact between the PCBs and the molten bath and to avoid localized 
cooling of the bath. 
As discussed briefly above, each of the compartments 38 and 40 of the 
charging port 26 also includes a suitable evacuation system (not shown) 
for removing any gases which may enter either compartment from the chamber 
18 or from the atmosphere. The evacuated gas from the compartments 38 and 
40 is preferably recycled back into the chamber 18 by any suitable means 
(not shown) to provide for the processing of any hazardous gas which may 
be present. Such an evacuation system may be of any suitable known type 
and need not be described in detail for a complete understanding of the 
present invention. 
Charging port 28 is similar to charging port 26, in that, it comprises a 
generally tubular sealed (gas-tight) passage 48 having an entry port 50, 
an exit port 52 and a partition means 54 to divide the passage 48 into a 
first outer compartment 56 and a second inner compartment 58. Both of the 
compartments 56 and 58 include an evacuation system (not shown) for the 
purposes described in connection with charging port 26. However, unlike 
charging port 26, the second compartment 58 of charging port 28 includes a 
conventional motor driven screw conveyor or auger 60. The screw conveyor 
60 transports the PCBs and the PCB containers received within compartment 
58 to the exit port 52 and for the reasons as stated above, punctures or 
crushes the capacitors or containers. 
The second compartment 58 of the inlet device 28 also includes a conduit 
means or drain pipe 62 for conveying the liquid PCBs from punctured 
capacitors (not shown) within the second compartment 58 to the molten bath 
22. However, unlike the previously discussed arrangement of drain pipe 44, 
drain pipe 62 empties directly into the molten bath 22 below the surface 
thereof. A suitable pump 64 is employed to provide enough pressure to 
"bubble" the liquid PCBs directly into the molten bath 22 as well as to 
control the flow rate of liquid PCBs into the bath. 
As discussed above, the immersion of the PCBs into the high temperature 
molten bath 22 results in the decomposition of the PCBs into gases which 
remain within the chamber 18 above the molten bath 22. As the gases come 
into contact with the high temperature upper surface of the molten bath 
22, the chemical bonds are further broken. By controlling the quantity of 
PCBs which are immersed into the molten bath 22 (i.e., through the use of 
valve 46 and pump 64), the quantity of the gases subsequently released 
into the chamber 18 and thus, the gas pressure within the chamber 18, may 
be controlled. The housing 12 should be strong enough to withstand a gas 
pressure of five atmospheres within the chamber 18 with no uncontrolled 
leakage of gas to the atmosphere. 
The furnace 10 also includes electrode means, generally designated 66, for 
maintaining a direct current (DC) electric arc within the chamber 18. The 
electrode means 66 comprises in part an elongated tubular electrode 68 
movably mounted to the furnace cover 70. The electrode 68 is moved 
vertically with respect to the molten bath 22 for the purpose of 
establishing and maintaining the desired electrical arc (shown generally 
as 72) extending from the arcing tip 82 to the molten bath 22. Any 
suitable means may be employed for the vertical movement of the electrode 
68. For example, a rack 74 may be fixed to the electrode and a suitable 
pair of motor-driven pinions 76 may be employed to engage the electrode 
rack 74 for movement thereof in either vertical direction. 
The furnace 10 also includes exhaust means, generally designated 78, for 
the removal of gases from the gas-tight chamber 18. In the present 
embodiment, the exhaust means 78 comprises the hollow interior of the 
tubular electrode 68 which communicates with a suitable exhaust conduit 80 
extending through the furnace cover 70 to atmosphere. However, it should 
be appreciated that any other suitable exhaust means (other than the 
hollow interior of the tubular electrode 68) could be employed for the 
removal of gases from the chamber 18. The only requirement for the exhaust 
means 78 is that its entrance be located proximate to the arcing tip 82 of 
the electrode 68, so that all of the gases within the chamber 18 must pass 
near or through the arc 72 before being exhausted from the furnace 10. 
The exhaust gas removed from the furnace 10 may be received and stored in 
suitable containers (not shown) for testing and analysis. If the analyzed 
gas is found to be clean enough to comply with existing regulations or 
standards, it may be exhausted directly to the atmosphere. If the analyzed 
gas is found to be of unacceptable quality, it may be further processed by 
a suitable device such as a bubble tank (not shown) or a scrubber (not 
shown). An exit gas afterburner (not shown) may also be employed. In the 
event that the exhaust gas from the furnace still contains toxic or other 
hazardous material, the gas may be recycled by any suitable means (not 
shown) back into the chamber 18 for further processing relative to the 
electric arc. Suitable heat exchange means (not shown) may be provided to 
lower the temperature of the exhaust gases from the furnace and to reclaim 
or recycle the recovered thermal energy. 
In order to provide a substantially continuous DC arc within the chamber 18 
between the arcing tip 82 of the electrode 68 and the molten bath 22, the 
outer shell 14 of the furnace is connected to ground (not shown) and the 
electrode is connected to a suitable low voltage, solid state DC current 
supply (not shown). Preferably, the DC current supply is so poled that the 
electrode 68 is negative with respect to the outer shell 14. The 
conductive inner lining 16 and the conductive molten bath 22 are also 
maintained at ground potential. Thus, the electrode 68 constitutes the 
negative terminal and the molten bath 22 constitutes the positive terminal 
of a DC load circuit. As shown, the two terminals (the electrode 68 and 
the molten bath 22) are spaced apart in operation to provide between them 
an arc gap of a predetermined distance in which the arc 72 exists when the 
circuit is energized. A current regulator (not shown) may be provided to 
maintain a substantially constant predetermined arc level as required for 
the desired decomposition of the hazardous material being processed. Arc 
voltage sensing equipment (not shown) may also be employed to compare the 
arc voltage with a preset reference for comparison and arc length control. 
A DC choke coil (not shown) may also be connected in series with the DC 
arc current path in order to prevent arc extinction due to any sudden rise 
in arc voltage, any sudden cooling of the arc due to endothermic chemical 
reactions, or to transient gas pressures which occur during PCB 
decomposition. 
The arc 72 provides the primary heat to initially melt and thereafter 
maintain the material within the sump in the molten state. The arc 72 also 
serves as a source of radiation, for example, ultraviolet radiation, which 
assists in breaking the bonds of the PCBs. In addition, the extreme high 
temperature of the arc (10,000.degree. C. or higher) assures that the 
gases and any previously non-decomposed material passing through or near 
the arc toward the exhaust means 78 and completely decomposed into the 
above-described generally innocuous gaseous elements. 
In order to further insure that the gases from the chamber 18 obtain 
maximum exposure to the arc for complete decomposition, the furnace 10 
also includes means, generally designated 84, for rapidly and uniformly 
moving the arc 72 in a predetermined path around the surface of the arcing 
tip 82 of the electrode 68. The rapid rotation of the arc 72 around the 
arcing tip 82 also provides a more uniform distribution of heat to the 
molten bath 22 and processing in the chamber 18 which tends to preserve 
the inner lining 16. The rotating arc also puts pressure on the molten 
bath material where the arc hits the molten bath 22, this together with 
the high temperature of the arc causes the material to boil and form an 
indentation in molten bath material. The rotation of the arc around the 
arcing tip 82 may be so fast that the indentation may not be refilled, and 
high temperature boiling material is spewed out in the vicinity of the 
indentation. The gases passing proximate the arc are contaced by the heat 
and the super heated bath material to aid in decomposition. 
In the present embodiment, the means for moving the arc around the surface 
of the arcing tip 82 of the tubular electrode 68 comprises magnetic means 
in the form of an annular electromagnetic coil 86 positioned within the 
housing 12 beneath the arcing tip 82. The electromagnetic coil 86 is 
connected to a suitable DC voltage source (not shown) to generate a 
magnetic field having flux lines (not shown) extending generally 
perpendicular to the arc 72. In this manner, well-known 
magnetohydrodynamics principles are employed to move the arc 72 around the 
surface of the arcing tip 82. The rate of movement of the arc around the 
arcing tip 82 is controlled by controlling the location of the 
electromagnetic coil 86 and the intensity and orientation of the magnetic 
field generated by the coil 86. The magnetic field also serves to stir the 
molten bath 22 to provide more complete mixing of the molten bath material 
and the hazardous materials which are being decomposed. In this manner, 
the upper surface of the molten bath 22 is kept in condition to receive 
and react with newly introduced hazardous material. 
As hazardous material and the various inorganic (metallic) containers 
associated therewith are added to the furnace 10, the level of the molten 
bath 22 tends to rise. In order to maintain the molten bath 22 at a 
predetermined depth commensurate with the size of the chamber, the length 
of the arc and other such factors, it is necessary to provide a means for 
removing some of the material from the molten bath 22 while still 
continuing the decomposition of the hazardous material. In the present 
embodiment, the means for maintaining the molten bath at the desired 
predetermined depth comprises a generally cylindrical container 88 
positioned beneath the center of the furnace housing 12. An annular weir 
90 is provided to establish the predetermined depth of the molten bath. 
Whenever the depth of the molten bath exceeds the height of the weir 90, 
molten material flows over the weir 90, through a conduit means or drain 
pipe 92 and into the cylindrical container 88. The conduit means 92 and 
the cylindrical container 88 are provided with suitable sealing means (not 
shown) in order to maintain the chamber 18 in the gas-tight condition. 
The cylindrical container 88 is removably attached to the furnace housing 
12. In this manner, material flowing from the molten bath 22 over the weir 
90 may be collected in the cylindrical container 88 until the cylindrical 
container is filled. The cylindrical container may then be removed from 
the furnace housing 12 and the material collected therein may be suitably 
emptied and/or disposed of in a covnentional manner. In order to ensure 
that the chamber 18 remains gas-tight during the period of time when the 
cylindrical container 88 is removed for emptying, a suitable sealing 
apparatus 94 is provided to close off the conduit means 92. A suitable 
evacuation system (not shown) may also be provided to remove any gases 
which may have accumulated within the cylindrical container 88. The gases 
removed from the cylindrical container 88 are recycled back into the 
chamber 18. By first sealing off the conduit means 92 with the sealing 
apparatus 94 and then employing the evacuation system to remove gases 
accumulated in the cylindrical container 88, the container 88 may be 
removed for emptying without affecting the continued operation of the 
furnace 10. Once the empty container is replaced, the sealing apparatus 94 
is again opened and molten material may again flow through the conduit 
means 92 for collection in the container 88. 
Alternatively, excess material may be removed from the molten bath 22 by 
means of a standard tap or drain (shown in phantom as 96). However, in 
order to utilize such a tap or drain 96, it is first preferable to halt 
the normal operation of the furnace 10. Material removed through the tap 
96 may be suitably disposed of in any conventional manner. 
As a variation of the above-described embodiment, the gases from the 
chamber 18 may be exhausted through the conduit means 92, into the 
cylindrical container 88 and out of an alternate exhaust conduit (shown in 
phantom as 81). In this manner, the gases may react with the material 
within the container 88 for further processing. 
Referring now to FIG. 2, there is shown an apparatus or furnace 110 for the 
decomposition of hazardous material which is substantially the same as the 
furnace 10 of FIG. 1. In connection with the description of FIG. 2, the 
same numbers will be used for the same components but with the addition of 
100 there to. Viewing FIG. 2, it can be seen that the furnace 110 
comprises a generally cylindrical housing 112 which defines a gas-tight, 
generally cylindrical chamber 118. Within the chamber 118 is a molten bath 
122 of metal, salt or any other suitable conductive material. A generally 
tubular electrode 168 is similarly movably attached to the furnace cover 
170. As in the furnace shown in FIG. 1, the center of the tubular 
electrode 168 comprises an exhaust means 178 which further includes an 
exhaust conduit 180 to permit the removal of gases from the chamber 118 to 
the outside of the furnace 110. The furnace 110 further includes suitable 
inlet means (not shown in FIG. 2) for introducing hazardous material into 
the chamber 118 in the same manner as was shown and described in 
connection with FIG. 1. 
The primary difference between the furnace 10 of FIG. 1 and the furnace 110 
of FIG. 2 is in the manner in which the excess material is removed from 
the molten bath. As shown on FIG. 2, a generally cylindrical container 188 
is provided adjacent to one side of the furnace housing 112. The adjacent 
side wall of the furnace housing 112 includes an opening which forms a 
weir 190 to establish the depth level of the material within the molten 
bath 122. Any material rising above the level of the weir 190 flows 
through a conduit means 192 and into the container 188. The container 188 
is removable from the conduit means 192 and both the container 188 and the 
conduit means 192 are provided with suitable sealing means (not shown) to 
preserve the gas-tight integrity of the chamber 118. A suitable sealing 
apparatus 194 is provided to close off and seal the conduit means 192 when 
the container 188 has been removed for emptying. A suitable evacuation 
system 198 comprising a suitable pump 200 and a corresponding check valve 
202 is provided to evacuate any gases which may accumulate in the 
container 188 prior to emptying the container. As shown, the gases removed 
from the container 188 are recycled back into the chamber 118 for further 
processing. 
A further difference between the furnace 10 of FIG. 1 and the furnace 110 
of FIG. 2 is in the location of the annular electromagnetic coil 186 which 
is employed to cause the rotation of the arc 172 around the arcing tip 182 
of the tubular electrode 168. As shown, the electromagnetic coil 186 is 
located on the outside of the housing 112 beneath the electrode 168. In 
order to insure that the housing 112 does not interfere with the magnetic 
field generated by the external electromagnetic coil 186, the lower 
portion of the housing is comprised of non-magnetic material as shown. As 
in the embodiment of FIG. 1, the flux lines from the magnetic field are 
perpendicular to the arc 172, thereby causing the arc to rotate around the 
surface of the arcing tip 182. 
FIG. 3 shows a slight variation of the furnace of FIG. 2, wherein the same 
numbers are used as appear in FIG. 2 but with the addition of primes 
thereto. In FIG. 3, the conduit means 192' for removing material from the 
molten bath 122' is positioned beneath the surface of the molten bath. The 
conduit 192' further includes a standard plumber's P-trap arrangement 104' 
to effectively prevent gases contained within the chamber 118' from 
entering the container 188'. A sealing apparatus 194' is also provided to 
facilitate the emptying of the container 188' without any interruption of 
furnace operation. 
FIG. 4 shows a different variation of the furnace of FIG. 2 in which a 
different means is provided for moving the arc 472 around the arcing 
electrode tip 482. Referring to FIG. 4, the same numbers are used as in 
FIG. 1 but with the addition of 400 thereto. In FIG. 4, instead of 
employing an electromagnetic coil, as was done in connection with the 
embodiment of FIG. 2, a first generally cylindrical ferrous member 406 is 
positioned within the hollow interior of the tubular electrode 468 
adjacent to the arcing tip 482. Similarly, a tubular ferrous member 407 
surrounds the tubular electrode 468 adjacent to the arcing tip 482. Both 
of the ferrous members 406 and 407 may be cooled employing a suitable 
known cooling system (not shown) which uses a heat transfer fluid such as 
water (not shown). The ferrous members 406 and 407 interact with the arc 
current to generate a magnetic field having flux lines (not shown) which 
extend generally perpendicular to the arc 472. In this manner, the arc is 
made to rotate around the surface of the arcing tip 482 in the same manner 
as was discussed in detail in relation to the apparatus of FIG. 1. 
Referring now to FIG. 5, there is shown a schematic representation of a 
pressure relief system generally designated 500 which may be employed in 
connection with furnace 10 of the type described in FIG. 1 or any of the 
above-described alternative furnace embodiments. The pressure relief 
system comprises a sealed (gas-tight) container or surge tank 502 located 
proximate to the furnace 10. A suitable first conduit means 504 extends 
between the furnace 10 and the sealed container 502 and provides 
communication between the interiors thereof. A pressure relief valve 506 
is positioned within the first conduit means 504 to control and effectuate 
relief of the pressure within the furnace 10, if necessary. As described 
above, the furnace 10 should be constructed to withstand an internal gas 
pressure of five atmosphere without leaking any gas therefrom. The 
pressure relief valve 506 should be designated to relieve the furnace 
pressure at a preset pressure point slightly less than the five atmosphere 
level. 
Once the preset pressure point of the pressure relief valve 506 has been 
exceeded the excess gas from the furnace 10 flows into the container 502 
thereby lowering the pressure within the furnace. A second conduit means 
508 and a suitable pump 510 are provided to return gas from the sealed 
container 502 to the furnace 10 for further processing when the pressure 
within the furnace has decreased to an acceptable level. 
From the foregoing description and the accompanying figures, it can be seen 
that the present invention provides a method and apparatus for the 
decomposition of PCBs and other hazardous material which is efficient, 
relatively easy to control and is very effective in operation. It will be 
recognized by those skilled in the art that changes or modifications may 
be made to the above-described embodiments without departing from the 
broad inventive concepts of the invention. It is understood, therefore, 
that this invention is not limited to the particular embodiments 
described, but it is intended to cover all changes and modifications which 
are within the scope and spirit of the invention as set forth in the 
appended claims.