CMPS&F - Environment Australia
Appropriate technologies for the treatment of scheduled wastes
Review Report Number 4 - November 1997
The CSIRO Division of Coal and Energy Technology in conjunction with TransGrid has developed a process for the regeneration of PCB contaminated transformer fluids (Duffy, 1994, 1997). The process is designed to both destroy residual PCBs in the oil and regenerate the oil for use as a dielectric fluid. The process also removes the oxidation products from the oil and reinstates the dielectric properties of the fluid.
The ability to reuse the treated transformer oil is a major advantage of this system, given that the cost of replacement fluid is in the order of $1400/tonne (Duffy, 1997). The principal effluent streams from the process are a waste water stream containing in the order of 400 mg/L of dissolved chloride (which, in some cases, can be discharged as a trade waste) and a gaseous emission which will be treated before discharge using a catalytic combustion process.
While very limited information is available regarding the treatment process, CSIRO claims the process is effective in:
CSIRO states that destruction efficiencies using this process compare with those achieved using high temperature incineration. However, CSIRO says that the potential to form and release dioxins is much lower in the CSIRO developed catalytic process.
To date, the process has only been demonstrated at a laboratory scale. However, a 1000 litres/day prototype unit is currently being operated in the laboratory at Lucas Heights (Duffy, 1997). The pilot plant work is seeking to provide the necessary information for implementation of the process on a commercial scale and to obtain reliable cost estimates. The pilot plant work is providing information on the catalyst life and the nature of the effluent streams. A process design study indicates that the process is technically feasible as well as being potentially economically competitive with other alternatives.
This phase of the development is aimed at optimising process conditions and plant design, and proving that the process will work on oils with a wide range of qualities. A large quantity of product oils are also being produced for further assessment in actual transformers, to determine the oil characteristics for reuse.
No specific cost data was provided by CSIRO, although the process design study concluded that the process would be competitive with other options for treatment of PCB contaminated oils. CSIRO reports that the experimental program will continue until mid-1997.
(a) Proponents (in Australia)
CSIRO Division of Coal and Energy Technology and TransGrid.
(b) Wastes Applicable
PCB contaminated transformer oils. Other organochlorine wastes may also be treated.
(c) Contaminants Applicable
PCBs, DDT, HCB and most likely other scheduled compounds.
To date, the process has only been demonstrated at a laboratory scale with a prototype unit currently treating up to 1000 litres/day. CSIRO reports that the experimental program will continue until mid 1997 (Duffy, 1997).
(e) Timing for Commercialisation in Australia
Expressions of interest for commercialising the technology were called for in late 1994. The CSIRO Division of Coal and Energy Technology expect to have a commercial size treatment unit operating by the end of 1997. Commercial arrangements for development of the technology are currently being negotiated in Australia, Japan, USA, Canada and Europe.
(f) Cost (example only)
No data were provided by CSIRO, although it is expected that this process will be competitive with other alternatives.
(g) Safety/Environmental Risk
Insufficient information is available to determine the risks. However, CSIRO notes that process conditions do not favour the formation of dioxins.
(h) Non-technical Impediments
Nil at this stage.
(i) Preferred Mode of Implementation
CSIRO intend to work with commercial operators on an exclusive or non-exclusive basis in various geographic regions (Duffy, 1997).
As limited information is available on this process, limitations cannot be determined at this stage.
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