Mineral oils: processes and products – Refining – Halogen contaminant removal
Patent
1982-10-29
1984-02-07
Davis, Curtis R.
Mineral oils: processes and products
Refining
Halogen contaminant removal
210909, 585469, C10G 1700
Patent
active
044302088
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The commercial introduction of polychlorinated biphenyls (PCBs) in 1929 represented a major breakthrough in the technology of dielectric fluids. These compounds were found to have outstanding thermal stability, resistance to oxidation, acids, bases and other chemical agents, as well as excellent electrical insulating characteristics making them ideal for applications in electrical capacitors and in high performance electrical transformers. PCBs gained rapid and widespread acceptance in the electrical industry.
In 1966, the discovery of PCBs in environmental samples stimulated concern over, and considerable research on their potential toxic hazards. By the early 1970's those hazards had become well recognized, and prompted major manufacturers of PCBs to restrict sales to applications in closed electrical systems. All production of PCBs was stopped in 1977.
During the 1970's the U.S. Environmental Protection Agency (EPA) set out to develop guidelines for control of PCBs. This effort culminated in publication of a series of regulations on PCBs handling and disposal requirements in the Federal Register on May 31, 1979 and Mar. 28, 1980. See also: "EPA's Final PCB Ban Rule: Over 100 Questions and Answers to Help You Meet These Requirements", Office of Toxic Substances, EPA, Washington, D.C. (June 1980). These regulations cover the maintenance, operation, and disposal of three classes of transformers, as follows: regulations.
These regulations have had particular impact on electrical utility companies. Although PCBs have not been used extensively in general purpose distribution transformers, cross contamination in transformer manufacturing and service facilities over many years has resulted in widespread appearance of relatively small amounts of PCBs in many transformers.
The development of acceptable procedures for operating under the EPA regulations has become the subject of intensive research. The principal effort has been directed toward development of safe and effective PCB disposal techniques. Until recently the only accepted methods of disposal were by dumping in rigidly designed safe land fills or burning in carefully controlled high temperature incinerators. However, lack of approved facilities has limited disposal capacity by these methods. Such methods are also wasteful and reslt in permanent decommissioning of transformers or destruction of valuable and relatively scarce dielectric fluids.
Because of their remarkable stability PCBs are not only resistant to biological degradation but also to most of the well-known chemical decomposition methods. Some chemical decontamination methods which have reportedly produced positive results suffer from one or more serious limitations. The most widely reported chemical methods for decomposing PCBs employ extremely reactive sodium compounds. Sodium in liquid ammonia has long been used for this purpose in analytical chemical laboratories. Other decomposition processes for PCBs which are claimed to be effective employ high surface sodium, sodium
aphthalene, and sodium naphathalide. These processes share some notable drawbacks. The reagents are difficult to prepare, expensive to ship and unstable in storage. Moreover, active sodium compounds are sensitive to oxygen and to water and therefore cannot be used reliably under field conditions.
A few combined chemical/physical methods of PCB disposal have also been reported. See: O. Hutzinger, et al., "The Chemistry of PCBs", CRC Press Cleveland, Ohio, (1974). For example, radiation can destroy PCBs under certain conditions, but the process is slow, inefficient and not readily adaptable to field use. Some polymers, such as chloroprene derivatives, have been used to absorb PCBs from oil but these also apparently have limited effectiveness because of very low absorption capacity and very slow absorption rate.
During the past several years the Franklin Research Center of the Franklin Institute, Philadelphia, Pa. has developed a proprietary system for stripping the chlorine substituents from PCBs
REFERENCES:
patent: 4284516 (1981-09-01), Parker et al.
patent: 4326090 (1982-04-01), Smith et al.
patent: 4337368 (1982-06-01), Pytlewski et al.
patent: 4351718 (1982-09-01), Brunelle
patent: 4353793 (1982-10-01), Brunelle
Nepier et al., "Evaluation and Development of Polychlorinated Biphenyl Removal Processes", Published Feb. 5, 1982 by Union Carbide Corp.
Pytlewski Louis J.
Thorne Edward J.
Davis Curtis R.
The Franklin Institute
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