Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
2000-08-18
2002-07-02
Griffin, Steven P. (Department: 1754)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C588S249000
Reexamination Certificate
active
06414212
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to methods for dehalogenation of polyhalogenated aromatics using alkali dispersion.
BACKGROUND OF THE INVENTION
Polyhalogenated aromatics such as polychlorinated biphenyls (PCBs) are toxic materials that have been widely used in the utility industry. Because of environmental and health concerns, the production of PCBs was banned in the late seventies and their use strictly regulated. Moreover, extensive programs to remove and destroy PCBs have been established.
Although, in the utility industry, PCBs are mainly found in PCB-made equipment such capacitors and power transformers, they are also found in contaminated mineral oil used in transformers switchgears and other electrical equipment. In PCB-made equipment such as power correction capacitors, the PCB level found in the dielectric fluid is usually near 100%. In power transformers however, the PCB level is in the range of 40 to 60% with the balance of the dielectric fluid being a mixture of chlorobenzenes. The level of PCBs in the PCB contaminated equipment (mainly transformer) is usually in the range of 50 to 1,000 ppm.
Although incineration has been the most commonly used means for the destruction of PCBs, a number of chemical processes have been developed as disposal alternative for this type of wastes. The scientific and patent literature provides an extremely broad array of processes aimed at dehalogenating organic halides. For example, U.S. Pat. No. 4,379,746 to Norman et al. discloses a process for the destruction of PCBs wherein the PCBs are continuously re-circulated in an inert liquid medium and a sodium dispersion reagent is injected into the circulating liquid. U.S. Pat. 4,639,309 to Lalancette et al. discloses a method wherein an inert surface is coated with a dispersion of sodium or potassium and said surface reacts with the halogen of a polyhalogenated hydrocarbon. Canadian Patent 2,062,054 discloses a method for the destruction of high level PCB liquid wastes using a combination of distillation and sodium dispersion reagent. U.S. Pat. No. 5,185,488 to Hawari et al discloses forming a sodium dispersion and adding askarel dissolved in a lower aliphatic alcohol. Other alkali based processes for the dechlorination of PCBs are described in U.S. Pat. Nos. 4,340,471 and 4,416,767 to Jordan; U.S. Pat. Nos. 4,514,294 and 4,592,844 to Layman et al; U.S. Pat. No. 4,853,040 to Mazur et al; U.S. Pat. No. 4,950,833 to Hawari et al; U.S. Pat. No. 4,377,471 to Brown et al; and U.S. Pat. No. 4,379,752 to Norman.
The use of chemical processes for the disposal of toxic chemicals is limited by economic and safety factors. As the concentration of the toxic contaminant in the waste stream increases the amount of reagent required to destroy the material increases making the process more expensive to operate. This results in an economically disadvantaged disposal option. Because of these factors, particularly in the PCB disposal business, chemical options for the disposal of this waste has been limited to concentrations below 10,000 mg/kg.
In addition to the economic disadvantage of chemical processes for the destruction of toxic wastes, heat generated by commonly known destruction reaction results in an increase in the reactants' temperature. The temperature increase usually surpasses the flash point of the media (normally mineral oil), creating a potentially unsafe condition.
SUMMARY OF THE INVENTION
The present invention utilizes a novel process for decontaminating a contaminated inert fluid which is contaminated with a low level of polyhalogenated aromatic while simultaneously decontaminating a material which is contaminated with a high level of polyhalogenated aromatic, by an exothermic polyhalogenated aromatic destroying reaction. The method comprises: (i) placing in a vessel (a) an inert solvent; (b) an alkali dispersion; and (c) the high level contaminated material; a second step of (ii) substantially contemporaneous with the conclusion of step (i), adding to the contents of the vessel the contaminated inert fluid in a quantity sufficient to maintain temperature of the contents below flash point of the contents; and (iii) allowing a reaction between the alkali dispersion and the polyhalogenated aromatics to proceed until the contaminated inert fluid and the material are decontaminated to produce decontaminated inert fluid.
In one embodiment, the method further comprises, during step (iii), removing a sample from the contents and analyzing the sample to determine whether all polyhalogenated aromatics are destroyed. In another embodiment, the method further comprises substantially contemporaneous or subsequent to steps (ii) and (iii), the steps of (iv) placing water in the vessel to neutralize the contents and (v) placing inert fluid in the vessel, in a quantity sufficient to maintain the temperature of the contents below flash point of the contents. In a further embodiment, at least part of the water is in the inert fluid.
A further embodiment teaches, during step (ii), contaminated inert fluid is added into the vessel in a quantity sufficient to maintain temperature of the contents below a temperature that would denature the inert fluid, and, subsequent to step (iii), recovering the inert fluid as useable inert fluid. In a related embodiment, the useable inert fluid is recovered by, subsequent to step (iii), allowing reactants to settle out of the inert fluid and subsequently recovering the useable inert fluid.
The method may further comprise, prior to steps (iv) and (v), adding clean inert fluid to further cool contents of the vessel.
The method may further comprise, prior to conclusion of step (i), air is displaced from the vessel. The air may be displaced with a non-combustible gas.
In an embodiment, the inert solvent is contaminated with a low level of polyhalogenated aromatic.
In another embodiment, the alkali dispersion is obtained from an alkali selected from the group consisting of lithium, potassium and sodium. The polyhalogenated aromatic may be selected from the group consisting of polychlorinated biphenyls, polybrominated biphenyls, halogenated benzenes, halogenated biphenyls, polychlorinated dibenzofurnas, chlordane and halogenated polynuclear aromatics. The polyhalogenated aromatic may be PCB. In a further embodiment, prior to conclusion of step (i), the contents are heated to about 90° C. In an embodiment, during step (ii), the temperature is maintained below about 140° C.
In an embodiment the inert solution is organic solvent. In a further embodiment, the organic solvent is mineral oil.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention describes innovative, economical and safe means for the simultaneous destruction of both high and low level polyhalogenated aromatics. The invention teaches methods for the simultaneous dehalogenation of polyhalogenated aromatics in both high and low level wastes using an exothermic chemical reaction and the use of low level polychlorinated aromatic contaminated oil and/or wet clean mineral oil as both cooling medium for the reacting mixture and as a material which is decontaminated in the process.
Although the method is described as applied to the destruction of PCBs using an alkali dispersion, the methodology employed is also applicable to other chemical processes. Since the method allows for absorbing the heat generated by a high level PCB reactions using low level contaminated fluids, the method can be applied to other exothermic decontamination reactions. Examples of such exothermic detoxification reactions include destruction of high level PCBs with a mixture of polyethylene glycol and potassium hydroxide, and destruction of Chlordane (or other chlorinated pesticides) with metallic sodium. Examples of other suitable polyhalogenated biphenyls and alkali dispersions which may be used to destroy them are set out below.
In one method of the invention, low level PCB contaminated mineral oil is pre-heated and loaded into a reaction vessel. Any air head is displaced to avoid a potentially explosive situation
Gonzalez Luciano A.
Kowalyk Henry E.
Sim Blair F.
Griffin Steven P.
Johnson Edward M.
Kinectrics Inc.
Nixon & Vanderhye
LandOfFree
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