Reduction and disposal of toxic waste

Toxic compounds, entrained in water, are dissociated in an electric arc (e.g. 12000.degree. F.) in an airtight chamber charged with oxygen; metal ions (M.sup.+) resulting from dissociation are recombined as gaseous oxides (MO.sub.x) which are educted from the chamber and disposed of.

This invention relates to treatment of a body of toxic waste liquid, to 
oxidize the metal constituent to a gaseous form (e.g. water vapor in the 
instance of hydrogen metal ions, carbon dioxide in the instance of carbon 
as the metal constituent, and so on) followed by disposal of the gases 
thus produced. 
Polychlorinated biphenols (PCB) is one of the greatest toxic waste problems 
prevailing today. This material is very toxic and extremely carcinogenic. 
There are hundreds of million gallons of this toxic material in various 
forms in the U.S.A., simply stored in drums and dumps for want of any 
better disposal method other than incremental incineration which is an 
expensive and incomplete mode of disposal, particularly in that 
incineration results in toxic ash and air pollution. 
There are other materials (e.g. dioxins) in the same class as PCB, all as 
various forms of toxic hydrocarbons. Sulphur, nitrogen, potassium and 
sodium and other harmful elements or compounds may also be involved 
representing sources of toxic or carcinogenic precursors and, at the very 
least, noxious gases such as sulphur dioxide and nitrogen oxides which are 
notorious pollutants resulting from mere incineration. 
The primary object of the present invention is to present a more complete 
method of disposing of toxic waste material which for the sake of brevity 
may herein be classified as toxic hydrocarbons containing metallic ions 
(hydrogen and carbon) capable of being oxidized. As mentioned above, the 
toxic material may contain other metal ions in combined form which for 
purposes of this disclosure are in the same class as the hydrocarbons. 
Specifically, it is an object of the present invention to break down the 
toxic compounds in an electric arc at an exceedingly high temperature in 
an airtight chamber in which oxygen is introduced, allowing the metal ions 
to be recombined as oxides in a gaseous state (e.g. water vapor, oxides of 
carbon, oxides of sulphur and so on) and the gases thus formed are 
continuously educted from the chamber so that they may be disposed of in 
different ways as will hereinafter be described.

One example of an overall, complete reduction system is shown schematically 
in FIG. 1. A pair of electrodes 10 and 11 are disposed within a 
substantially airtight chamber 12. Chamber 12 will be jacketed in 
insulation, not shown. The electrodes are consumable, carbon or graphite 
for example, and the gap separation is such that the resultant arc, when 
current is applied, will produce a temperature in the neighborhood of 
12000.degree. F. to 16000.degree. F. 
An oxidizing atmosphere (preferably pure oxygen) is introduced into the 
chamber through a suitable conduit 14. Alternatively, or concurrently, 
oxygen may be introduced to a metering and mixing pump, via conduit 14A, 
hereinafter described. 
One of the electrodes, as will be shown, has a longitudinal bore opening at 
the arc gap. The toxic material, contained in a body of water (from 
storage) is fed from a mixer 17 (metering and mixing pump) to the bore or 
passage of the electrode by way of conduit 16 so that a jet of toxic 
material is emitted at the electrode gap where the metal constituents are 
oxidized. The term "metal" used herein is used strictly in the chemical 
sense, namely, a positive ion from the atomic table. 
The feed solution or mixture containing the toxic material is fed to the 
mixer 17 from storage via conduit 18 and oxygen may be fed to the mixer 
concurrently to aid mixing. A reagent may be fed to the mixer 17 through 
conduit 19 for reasons to be explained. 
The oxides formed within chamber 12 are educted by way of a conduit 20 and 
fed to a second airtight chamber 22 within which a second electric arc is 
established between a pair of consumable electrodes 24 and 25. Here, in 
chamber 22, any solid particles that may be carried over from chamber 12 
(e.g. graphite fragments) are themselves disintegrated or fractured to 
even smaller size within the high temperature arc 
(12000.degree.-16000.degree. F.). 
Any small particles solids within chamber 22 (carbon or graphite particles 
from the electrodes, particles resulting from reagent action, and the 
like) are of extremely small size and may be educted through a conduit 26. 
The effluent from chamber 22 is fed to a solids trap 28 and any remnant 
gas (e.g. Cl.sub.2, SO.sub.2) is subjected to a gas (aqueous) scrub in 
chamber 30. Harmless gases are finally fed from the scrubbing chamber 30 
to a stack 32. The stream of oxygen admitted to chamber 12 is under 
pressure and serves as the driving force to educt the chambers. 
The reagent admitted to the mixer is to assure that any ions not oxidized 
in chamber 12 may be combined anew. The chlorine ions in PCB (chlorinated 
hydrocarbons) for example may be recombined as NaCl by using NaOH as a 
reagent; silicon or iron may be recombined as a ceramic by using borax as 
a reagent. 
FIG. 2 presents more details of the equipment associated with the first arc 
chamber 12. A few variations, variants of what was described above in 
connection with FIG. 1, are also shown in FIG. 2. 
The gap 40 between the electrodes 10 and 11 should remain constant as the 
electrodes are consumed. Consequently the gap is monitored and the 
electrodes adjusted longitudinally to maintain a substantially constant 
gap. The gap may widen due to erosion of the cathode 11. Its position is 
monitored by an optical sensor including a lens 42 and photocell circuitry 
43; amplifier 44 emits a resultant signal indicative of an unacceptable 
wide gap, delivered to a servomotor 46 dedicated to maintaining a datum 
position for the lower electrode. 
Electrode 11 (cathode) is coupled to a feed nut 48 in turn threadedly 
associated with a feed screw 50 turned by the servomotor 46, advancing the 
electrode 11 to reposition it. 
The upper electrode 10 (anode) is to be constantly positioned for arc 
stability, unlike the lower electrode (cathode) which is adjusted to 
maintain a fixed or datum position. In this connection it will be 
recognized that the upper electrode or anode is a source of positive ions 
in the sense of an electrical current (not chemical sense) while the lower 
electrode or cathode is a source of electrons. Because of this difference, 
the lower electrode is consumed at a considerably less rate compared to 
the upper electrode. 
To adjust the upper electrode for arc stability, it is also coupled to a 
feed nut, nut 54, in turn threadedly mounted to a feed screw 55. The feed 
screw 55 is controlled by a servomotor 56. The servomotor 56 is dedicated 
to maintaining arc stability and under the control of a current sensor 58. 
To prevent instability of the arc and the possibility of extinguishing the 
arc, both the gap and the current should be relatively fixed or constant. 
Positioning of the cathode, incidental to its erosion, has been explained 
above. Since the anode is consumed at a greater rate, tending to lengthen 
the gap, this causes a decrease in the arc current, sensed at sensor 58, 
and resulting in a corresponding extension of the anode electrode to 
reduce the gap by way of the servomotor 56 and its screw 55. Thus, the 
current is responsive to arc performance. Unexpected fluctuations in the 
current can also result in repositioning of the anode by way of the 
servomotor 56. 
As shown in FIG. 2, the electrodes are provided with water-cooled 
frictional terminal clamps to which the power lines are connected, these 
clamps being identified by references characters 10C and 11C. 
Sensor 58 also senses or measures the power load of the arc and is used to 
adjust the metering pump rate to a near minimum which prevents flooding of 
the gap. 
Experience alone, with the particular source of toxic material, will 
establish the appropriate arc gap current and the related rate of feeding 
the body of liquid containing the toxic material. When the gap distance 
and current values are established, sensors 42-43 (optical) and 58 (arc 
gap current) are set and the feed rate established. Thereafter, sensor 
42-43 will assure that the eroding end of the cathode remains in its datum 
position, while sensor 58, sensing the prevailing current, will deliver 
signals to servomotor 56 appropriately to adjust the upper electrode to 
maintain a stablized arc. At the same time, sensor 58 sets the rate for 
the metering pump 17, which, of course, is a variable rate pump. 
As noted above, electrode 11, FIG. 3, is provided with a longitudinal bore 
identified in FIG. 3 by reference character 62. The upper end of the bore 
or passage 62 opens at the gap end of electrode 11. The lower end of 
passage 62 is coupled to conduit 16 which directs the flow of toxic 
material to passage 62. 
The introduction of oxygen by way of conduit 14 (or 14A) FIG. 1, is under 
pressure sufficiently to force the generated gases, resulting from 
dissociation of the toxic compound in the arc, out of chamber 12 into the 
educting conduit 20. Entrained in this flow of gases there may be tiny 
particles resulting from the electrode erosion. Also, there may be solid 
particles that may have been entrained in the body of liquid containing 
the toxic material, and there may be solids resulting from reagent action. 
These particulate bodies, though tiny, may be further disintegrated in the 
second chamber 22, FIG. 1. The stream of oxygen under pressure admitted to 
chamber 12 is also adequate to force the stream of oxide gases and 
entrained particulate material out of chamber 22, through conduit 26 to 
the solids trap 28. The educted stream continues to the scrubber 30 as 
explained above; here such readily soluble gases as SO.sub.2, Cl.sub.2, 
NO.sub.x and so on are removed. It may be mentioned at this point, 
however, that the second chamber 22 and the associated systems downstream 
thereof are not absolutely essential in practice. It may be sufficient 
under most circumstances simply to educt the gases and disintegration 
products from chamber 12, scrub the water soluble gases and permit any 
solids to settle. 
The basic principle is that the electric arc in chamber 12 has enough power 
to dissociate the toxic compound into its constituent ions. The metal ion 
(M+) is transformed to a gaseous oxide in the highest state of oxidation 
(MO.sub.x). If needed, a reagent is supplied to recombine the negative ion 
(e.g. Cl.sup.-) resulting from dissociation. Sensors are used to assure a 
substantially stable arc, a substantially fixed position for the cathode 
and rate of feed of the toxic compound that will not drown or quench the 
arc. If need be, solid particles educted from chamber 12 may be fractured 
to even smaller size in a second electric arc. Hence, while I have 
illustrated and described preferred embodiments of my invention, it is to 
be understood these are capable of variation and modification. 
Metallic electrodes may also be used. These may contain slag formers 
(coated electrodes) or other reactive coatings to take the place of or to 
supplement the reagent introduced at 19. Preferably a cathodic sputter 
shield or grid is placed at the arc zone area, reference characters 64 and 
65, FIGS. 1 and 2.