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CMPS&F - Environment Australia
Appropriate technologies for the treatment of scheduled wastes
Review Report Number 4 - November 1997


13. PLASMA ARC SYSTEMS


 

13.1 General

Plasma arc treatment is a high energy technology able to treat a range of scheduled wastes. In plasma arc treatment a thermal plasma field is created by directing an electric current through a low pressure gas stream. Plasma arc fields can reach 5000 to 15000oC. The intense high temperature zone can be used to dissociate the waste into its atomic elements by injecting the waste into the plasma, or by using the plasma arc as a heat source for combustion or pyrolysis.

The plasma arc processes considered in this review include:

13.2 PACT Process

13.2.1 Technology Description

The Plasma Arc Centrifugal Treatment (PACT) process, developed by Retech (USEPA, 1992 and Thomas, 1994), uses heat generated from a plasma torch to melt and vitrify solid feed material. Organic components are vaporised and decomposed by the intense heat of the plasma and are ionised by the air used as the plasma gas, before passing to the off-gas treatment system. Metal-bearing solids are vitrified into a monolithic non-leachable mass.

The PACT system comprises thermal treatment and exhaust gas treatment systems, shown conceptually in Figure 13.1. The thermal treatment system consists of:

The exhaust gas treatment system consists of:
Figure 13.1
Plasma Arc Centrifugal Treatment System
(USEPA, 1992)
Figure 13.1
The waste is initially loaded manually, from sealed containers, into a screw feeder. The waste is fed uniformly and continuously into the centrifugal reactor through a chute connecting the feeder to the primary chamber, which is a rotating tub with a central orifice.

A copper throat, at the bottom of the primary chamber, is used to strike the arc of the plasma torch. The torch is then moved slowly up and down the side of the primary chamber during heat up. Feeding the waste material begins once the primary chamber's temperature is greater than 1100oC and the secondary chambers temperature is greater than 900oC. Solid material is retained in the tub by centrifugal force. The primary chamber walls have an inner shell with a water jacket welded between. A water/corrosion inhibitor cooling stream circulates between the shell and the jacket.

The plasma torch uses electrical discharges to add energy to plasma torch gases in order to increase the gas temperature beyond that normally attainable by chemical reaction. The plasma torch produces a transferred arc that directly contacts a conducting portion (copper throat) of the centrifugal reactor. The heat generated by the plasma torch brings the waste material to temperatures sufficient to melt soil (typically in the order of 1650oC). The waste is melted by this extreme heat, incorporating any inorganic and metal components into a stable material. Organic components are volatilised by the heat of the plasma gas. Oxygen may also be added, via an oxygen lance in the primary chamber, to enhance combustion of organics.

The torch runs on direct current provided by a 3-phase power supply and is cooled by a high velocity flow of distilled water.

After the feed material adjacent to the copper throat is heated to the conducting temperature, the torch is moved slowly to heat more of the waste on the bottom of the reactor and eventually the sidewall. As the torch is moved away from the centre of the reactor, the rotation is slowed to allow the molten waste to run towards the centre, where it begins to solidify. This is continued until the entire primary chamber has been treated by the torch.

Once the complete primary chamber has been treated, the torch is then used to melt the mass of waste at the copper throat. When the mass is melted, the reactor spin rate is slowed to allow the pool to move inward and the melted waste to pour out of the bottom of the reactor through the throat, past a natural gas afterburner. The afterburner does not operate during the pouring process.

The afterburner, located just downstream of the primary chamber, provides an additional heat input beyond that supplied by the plasma torch to combust products (typically short chain organics) of incomplete combustion (PICs). The afterburner operates on a natural gas flame. The use of a secondary combustion chamber was required by the USEPA (as with high temperature incineration) to ensure complete combustion and destruction, particularly of dioxins and similar components. The organics that are volatilised and oxidised (or combusted) are drawn off to the gas treatment system.

A camera port in the secondary chamber allows observation of the gases and slag exiting the throat. If needed, oxygen may be added from oxygen jets located in the secondary chamber to enhance combustion of organics. The secondary chamber walls have 7.52 cm of refractory lining to abate heat loss and protect the steel walls. These walls also form a jacketed vessel with cooling water circulating between them to maintain a safe operating temperature.

The molten mass falls from the secondary chamber into a heavy pig mould located in the collection chamber. The collection chamber is a cylindrically shaped, water-cooled, jacketed vessel. One end is closed off and the other end has a hinged door, where the pig moulds are loaded and unloaded.

Effluent gas treatment equipment is designed to suit requirements of the feed material. A typical gas treatment system can comprise a quench tank, a jet scrubber, a packed-bed scrubber, and a demister.

A mildly caustic scrubber solution (pH maintained at 8.5) is used in the quench tank, jet scrubber, and packed-bed scrubber. The scrubber sump is equipped with a chiller to cool the scrubber water circulating through the exhaust gas treatment equipment, so that all the moisture can be removed from the exhaust gases. The chilled scrubber water proceeds first to the quench tank, where it cools the exhaust gas stream from approximately 540oC to 4oC. From the quench tank, the scrubber water passes to a jet scrubber, which is designed to remove particulates and acid gases. A counter-flow packed bed scrubber provides additional removal of acid gases. A demister then removes moisture droplets entrained in the flow.

The system is hermetically sealed and operated below atmospheric pressure to prevent leakage of process gases. Pressure relief valves connected to a closed surge tank provide relief if gas pressures in the furnace exceed safe levels. Vented gas is held in the tank and recycled into the furnace.

The clean gases are emitted to the atmosphere through an exhaust stack. A stack blower at the exhaust stack maintains a negative pressure in the reactor system, preventing any leakage.

The PACT process has been developed by Retech and is available in a range of sizes, relating to the diameter of the primary chamber in feet. ie. 2 ft, 4 ft, 6 ft and 8 ft. Retech's licensee in Europe is MGC Plasma AG of Basel, Switzerland who is now wholly owned by Moser Glaser AG a large Swiss transformer manufacturer (Zissermann, 1996).

The 6 ft PACT is undergoing extensive evaluation at the US Department of Energy's (DOE's) Western Environmental Technology Office in Butte, Montana. MSE Inc is the engineering company involved in the evaluation.

MGC Plasma AG has erected and trialed an 8 ft diameter unit which in Europe has the trade name "Plasmox". The major components of this unit, such as the primary and secondary chambers and the control panel, have been procured by MGC Plasma from Retech, but much of the equipment (particularly the gas cleaning equipment) was designed and sourced in Europe. An 8 ft unit has also been sold to the German Army for the clean-up of soil contaminated with chemical warfare agents, many of which are arsenic compounds. The 2 ft and 4 ft units can be made readily relocatable by being designed to fit within standard container-sized modules. The 6 ft and 8 ft units are more suited to a fixed installation.

13.2.2 Performance

The results show that:

The process has been demonstrated successfully under the USEPA SITE program, with the treatment of a mixture of 28000 mg/kg zinc oxide and 1000 mg/kg HCB in diesel oil. destruction and removal efficiency (DRE) exceeded 99.996% (HCB was not detected in the stack gas) and the treated material met TCLP requirements. Particulate emissions in the test did not comply with the regulatory standard and the off-gas treatment system was to be modified accordingly. Particulate emissions from a PACT system in Muttenz were well within the US regulations. Dioxins were not detected in the stack gas (USEPA, 1992).

13.2.3 Considerations in the Application of the Technology

The PACT system has the ability to accept a wide range of waste materials, including large solid articles, and as such can be regarded as a flexible treatment system. The system can be applied to wastes containing both organics and heavy metals. In this regard the process has been referred to as "omnivorous".

Given the large thermal mass of the system, the risk associated with short term upset is likely to be low. Similar to in-flight plasma systems, the volume of gases produced in the process are much less than in incineration systems. It has been calculated that for a highly chlorinated waste such as hexachlorobenzene, PACT should produce gas volumes less than 2% of the volume of an incinerator of equivalent capacity (Selinger, 1995). If secondary combustion is required, this can add to the gas volume.

Given that the system can operate under pyrolytic conditions and a reducing atmosphere, dioxin formation in the primary chamber can be avoided. However, as it is usual to follow primary combustion with a secondary combustion step, there is a potential for dioxins to form and the provisions normally applied to incineration to minimise dioxin formation should also be applied to this system. Given the total air emission volumes are less than for conventional combustion processes, the potential impact of emissions is expected to be lower.

Treated soils and other materials from this process are generally converted into ash and as such can be returned to the site.

The PACT system can be expected to have a relatively high capital cost, and operating cost ($4000 - $8000 per tonne). However, the cost will be dependent on the scale of operation, and because the PACT process has the capability of directly treating diverse waste types, it can avoid the preparation or pretreatment costs which may otherwise be necessary for treatment by other processes.

13.2.4 Experience and Availability in Australia

While not established in Australia, the PACT system has been developed to a commercial scale for use overseas, and draws on established principles of combustion engineering. For the purposes of this review it is considered to be a developed process, although the requirement for trials means several years would be required for establishment of a full scale system in Australia. The implementation of the PACT process is linked to the limited number of major hazardous waste projects in Australia being progressed. For example, implementation of the PACT process has largely been discussed in terms of application to the treatment of HCB waste held by ICI at Botany (although a decision regarding treatment of this waste is yet to be made).

PACT technology has been selected for the clean-up of Pit 9 at the US DOE's Idaho National Engineering Laboratory. Pit 9 contains organic, inorganic and radioactive wastes. The consortium to undertake the work includes Lockheed Martin and MSE Inc. (Zissermann, 1996).

13.2.5 Summary

(a) Proponents (in Australia)

Waste Service NSW (Sydney).

(b) Wastes Applicable

All waste types, although concentrated wastes preferred on economic grounds.

(c) Contaminants Applicable

All scheduled compounds.

(d) Status

The PACT system is not yet established in Australia, however, it is operational on a commercial scale in Europe and in the US.

(e) Timing for Commercialisation in Australia

A commercial scale plant has been established in Europe and a similar plant is available in the USA. Establishment of the process within Australia could be achieved within a short time frame, if commercial viability was established and prompt regulatory approvals were obtained. Trials on Australian wastes were proposed for evaluation in the USA in 1995, however, these have been delayed (Zissermann, 1996).

Establishment of the process in Australia will depend on the waste volume requiring treatment and the available competing processes. In particular, implementation of the PACT process is likely to be dependent in its selection for use in one of the few major waste treatment projects in Australia that could justify the capital expense associated with implementation in Australia.

(f) Cost (example only)

Approximately $4,000-$8,000/tonne

(g) Safety/Environmental Risk

Operational experience in Europe has not identified specific problems. The absence of combustion gases means that gaseous emissions are much smaller than for high temperature incineration. A surge tank is provided to contain any uncontrolled release of gases from the treatment chamber. The use of mechanical seals and operation of the unit at slight negative pressures should ensure there are no significant fugitive emissions. The vitrified nature of the slag greatly reduces any potential leaching of metals or other residual contaminants. The available data indicates compliance with regulatory requirements regarding air emissions can be achieved and dioxins were not detected in the stack gas during trials under the USEPA SITE program.

(h) Non-technical Impediments

Information on this issue was not provided by the proponent. While the process includes some elements of combustion, it is likely to be viewed as sufficiently different from high temperature incineration by the public.

(i) Preferred Mode of Implementation

A centralised system is preferred. However, the PACT process is transportable in smaller plant sizes ie. a 2 ft diameter PACT system will fit into 2 x 20 ft long standard ISO shipping containers.

(j) Limitations

Removal of volatile metals and particulates which are formed from inorganic components of the waste (such as drums) may require removal by a conventional gas scrubber or gas cleaning system. Provision of either of these additional treatment steps may in turn add additional costs to this treatment process.

The PACT system is expected to have a relatively high capital and high operating cost, however, the final cost of treatment will depend on the overall scale of the operation. As the process is able to directly treat diverse waste types, pretreatment is not usually required and cost savings may result.

13.3 PLASCON

13.3.1 Technology Description

CSIRO and Siddons Ramset Limited have developed PLASCON, an in-flight plasma arc system. This technology was designed to treat process wastes from chemical manufacturing by using a high temperature electric arc plasma destruction technique (Hawkes, 1994a). SRL Plasma Limited (a division of Siddons Ramset Limited) has the full commercial rights to this process.

In the PLASCON system a liquid or gaseous waste stream together with argon is injected directly into a plasma arc, which provides plasma/waste mixing temperatures in excess of 3000oC. At these temperatures organic material is pyrolysed. That is, the organics in the waste dissociate into elemental ions and atoms and recombine in the cooler area of the reaction chamber prior to a rapid, alkaline quench to form simple molecules. The resulting end products include gases consisting of argon, carbon dioxide and water vapour and an aqueous solution of inorganic sodium salts (including sodium chloride, sodium bicarbonate and sodium fluoride) (Frost, 1995). Further treatment of the end product is not required.

In the order of 1 to 3 tonnes/day of waste can be treated by a 150 kW unit. The residence time of the waste in the reaction chamber is very short (approximately 20-50 milliseconds) since such high operational temperatures are utilised. This results in a small process inventory, with less than 0.5 g of waste being destroyed at any instant (Frost, 1995).

Electricity is the main energy input into the process. A 150 kW PLASCON unit requires 1000 to 3000 kWh of electricity per tonne of waste and 250 to 400 kW of cooling duty. Cooling is provided by a closed loop water circuit (Frost, 1995).

Plasma technology has been described as a "robust" technology which can be readily tailored to suit a specific application. This is accomplished by specifically designed front and back ends (ie. pretreatment systems and gas treatment systems) to suit a particular waste type (Hawkes, 1995).

The waste stream to be treated must be a liquid or a gas, however, any form of preprocessing which will produce a liquid or a gas can be used upstream of the PLASCON process unit. For example, contaminated soil and very viscous liquids or sludges thicker than 30 to 40 weight motor oil cannot be processed by the system without pretreatment (Frost, 1995). In this regard SRL Plasma has adopted a different approach to that adopted by many technology vendors. Processes such as BCD and Eco Logic have been promoted in a configuration that includes pretreatment for specific wastes. The focus of SRL Plasma is to develop solutions and license their technology to other parties. Only in limited cases will SRL Plasma operate their own plant. SRL Plasma suggest that a plant tailored to a specific application can be designed, built and be in operation in a period of about six months (Hawkes, 1995).

On this basis, while PLASCON is not currently available in a configuration capable of treating a range of waste types (eg. contaminated soil, capacitors, etc.) PLASCON, in conjunction with appropriate preprocessing (eg. thermal desorption) could treat a wide range of wastes.

It can be expected that the unit will be implemented as a relocatable centralised facility rather than a portable system which is moved from site to site (Hawkes, 1994 b).

The PLASCON unit is shown schematically in Figure 13.2.

13.3.2 Performance

Test samples of PCBs made up from an Askarel type oil containing Aroclor 1260 and trichlorobenzenes in the ratio of 65:35 which were treated in a bench scale plasma arc unit showed dioxin levels in scrubber water and stack gases in the part per trillion range. The Aroclor 1260 mainly contains hexachlorinated (42%) and heptachlorinated (38%) biphenyls. DREs in the test ranged from six to eight nines confirming in-flight plasma systems can achieve very high destruction efficiencies. Dioxin formation is generally avoided in in-flight systems such as PLASCON, because the process involves pyrolysis rather than combustion (Frost, 1994).

The PLASCON process has been in operation since 1992 at Nufarm Limited. The Nufarm plant, used in-line for treating process wastes, is approved by the EPAV and is commercially viable.

13.3.3 Considerations in the Application of the Technology

Plasma arc treatment involves a much lower quantity of combustion gases than incineration, thus reducing the risk associated with the discharge of the emissions to air and the cost of air pollution control. Given the very low process inventory in the PLASCON system (ie less than 1 g in the reaction chamber), the risk associated with release of partially treated wastes following a process failure is very low (Hawkes, 1994a).

Significantly reduced emissions count in favour of plasma arc systems, and this process is not associated with the level of community concern which accompanies incineration systems.

In-flight plasma arc treatment processes are applicable for liquid and gaseous wastes, and in general are not applicable to solid wastes unless there is some form of pretreatment undertaken. As such, in-flight plasma arc systems are usually discussed in the context of direct treatment of liquid or gaseous wastes. Plasma arc treatment can be linked with thermal desorption, and would have the potential to provide relatively complete destruction of contaminants in solid and semi-solid materials.

Figure 13.2
PLASCON Treatment System
(Hawkes, 1994a)
Figure 13.2

13.3.4 Experience and Availability in Australia

PLASCON has, to date, treated wastes including (Frost, 1995):

SRL Plasma is currently focusing on expanding its operating experience to a wide range of scheduled wastes.

The PLASCON system is operating at Nufarm, a herbicide manufacturing works in Laverton, Victoria. This is the first Australian commercial PLASCON facility. It has been in operation since early 1992 and was licensed by the EPAV in 1993. The plant operating currently at Nufarm is a 150 kW system. This facility is being used to treat totally organic waste containing a variety of organochlorine compounds, on a small throughput basis. Typically, the waste averages 30% w/w of chlorine. A second PLASCON unit has been commissioned to cope with the increased plant throughput (200 kW system).

The waste treated by PLASCON at Nufarm is moderately viscous, with a high concentration of chlorinated organics, and a solids content of 40%. Extensive research and development including several modifications to the Nufarm plant has resulted in a PLASCON unit that can reliably treat the waste. SRL Plasma indicates that the development of the plant at Nufarm has meant that it has tackled and solved many difficult problems that would streamline the development of new applications (Hawkes, 1995).

The PLASCON system is being used to treat the Nufarm waste on a continuous or semi-continuous basis.

A new installation for Ozone Depleting Substances 1 destruction using PLASCON technology has been constructed. The facility is owned and operated by SRL Plasma for the purpose of destroying the waste Halon and CFC stockpile held by the Department of Administrative Services Centre for Environmental Management (DASCEM), which administers the National Halon Bank on behalf of the Federal Government. This unit has destroyed significant quantity of Halon wastes and is currently operating on a two shift basis. Within a short period of time SRL Plasma Limited expect to operate an "unmanned" third shift which will have interlocks within the process to ensure safe shutdown in the event of any system failure.

SRL Plasma has also reached an agreement to provide the PLASCON technology for use by BCD Technologies in Brisbane. It is understood that the PLASCON unit is currently under construction and will be commissioned in mid-1997 (Krynen, 1997). A six month trial and demonstration licence has been obtained for the system. BCD Technologies view the PLASCON systems as an important adjunct to their established waste treatment capabilities using the BCD process. In particular, BCD Technologies intends to make use of the PLASCON unit for the treatment of high strength wastes such as pure PCB liquids. Such wastes are not well suited to treatment using the BCD process (although the BCD process is well suited to the treatment of PCB contaminated transformer oils). Currently BCD Technologies is treating small quantities of pure PCB liquids by blending with dilute, PCB contaminated oils. BCD Technologies is also considering linking the PLASCON unit with a thermal desorber for the treatment of a range of solid and semi-solid waste streams. This should result in a significant new treatment capacity for scheduled wastes in Australia.

BCD Technologies had delayed the decision to implement a technology such as PLASCON, based on the assumption that the Eco Logic facility in Western Australia would have sufficient capacity to meet the requirement for treatment of high strength PCB wastes in Australia. The decision by BCD Technologies to purchase and implement the PLASCON technology for the treatment of PCB wastes reflects the failure of the Eco Logic process to live up to earlier claims regarding treatment capability and capacity.

PLASCON technology is available for both in-line and stockpile applications. PLASCON markets are currently being pursued both domestically and internationally.

13.3.5 Summary

(a) Proponents (in Australia)

SRL Plasma Limited (a division of Siddons Ramset Limited). In addition, BCD Technologies has purchased a PLASCON unit from SRL Plasma which will be available for treating a range of wastes.

(b) Wastes Applicable

Liquid waste streams (either organic or aqueous) of any concentration can be treated but it is most cost effective to treat concentrated wastes. Solids can be treated if in the form of a pumpable fine slurry. The system can be linked with thermal desorption or other pretreatment methods to treat a wide range of solids and sludges. Special wastes such as capacitors and transformers can be treated after pretreatment to remove solids.

(c) Contaminants Applicable

All scheduled compounds.

(d) Status

Commercially available and operational in Australia both as in-line and stand alone configuration. A PLASCON system is currently operating at Nufarm in Laverton, Victoria. A second PLASCON system is currently being used to destroy stockpiled CFCs and Halons. A PLASCON system will shortly be available through BCD Technologies for the treatment of a range of wastes, including high strength PCB wastes.

(e) Timing for Commercialisation in Australia

Currently available as an in-line system. The PLASCON unit purchased by BCD Technologies is expected to be commissioned in the second half of 1997.

(f) Cost (example only)

Operating costs including labour vary depending on the work to be treated and the location of the site. These costs are estimated to be under $3000/tonne but typically range from $1500 - $2000/tonne. SRL Plasma indicate (Hawkes, 1994a) that there is a considerable range of cost depending upon factors such as:

SRL Plasma indicate that the economics of the process are not sensitive to chlorine content of the waste (Hawkes, 1995).

(g) Safety/Environmental Risk

A significant advantage of the PLASCON system is the low process inventory. The process is electrically powered and can be shut down or started up in seconds. Process control interlocks are provided to prevent the release of incompletely treated waste, in the case of power failure or similar process upset. Other safety hazards relate to the storage of hazardous materials prior to treatment and the use of high temperatures. Emissions from the treatment system are limited to an emission to air containing argon, oxygen, water vapour and carbon dioxide, and a trade waste discharge containing a sodium halide salt. Dioxin formation is avoided by the use of pyrolysing conditions.

(h) Non-technical Impediments

Nil.

(i) Preferred Mode of Implementation

A centralised or relocatable unit.

(j) Limitations

Only able to treat liquids and gases. Solids can only be treated following extraction using another technology or by formation of a fine pumpable slurry.

13.4 STARTECH

13.4.1 Technology Description

The STARTECH Plasma-electric Waste Converter (PWC) was developed in the US by the Startech Environmental Corporation. The system was designed to treat wastes, both hazardous and non-hazardous. Startech has an agreement with Zealmore Pty Ltd for the sale and installation of Startech Plasma Waste Converters in Australia (Schallhammer, 1997).

The Plasma Waste Converter forces gas through an electrical field to ionise the gas into a plasma. The plasma operates at temperature in the order of 3,000 to 5,000oC. The plasma chamber operates at normal atmospheric pressure. The PWC may best be described as a plasma heated pyrolysis system, where wastes are reduced to their metallic components, a slag and a gas that can be used as a fuel. In this respect the STARTECH system is more similar to the PACT technology than the PLASCON technology, although it operates in an oxygen deficient or reducing atmosphere.

Organic and inorganic wastes can be introduced into the plasma chamber as solids, liquids, gases, and sludges, where they dissociate into their elemental atomic components. Gas recovered from the top of the chamber is treated and can be reused as chemical feed stock or fuel gas. Molten solids are removed from the bottom of the chamber and can also be reused.

Solid wastes fed into the system do not ordinarily need to be pre-conditioned or shredded, and can be in bulk form. Feeding is automatic through an air locked infeed port and is normally on a continuous basis, but can be batch fed. Liquids, gases and sludges can also be fed or pumped directly into the chamber through a pipe port, and can be fed in with bulk solids at the same time if required.

The STARTECH Plasma Waste Converter is a closed-loop system in which wastes, depending on their type, may be converted into recoverable commodity products. Recovered gas, "Plasma Converted Gas", may be used for chemical feed stock to produce, for example, polymers, or fuel gas for plant heating or to produce electricity. Recovered solids include metals, and an inert silicate stone which can be used as aggregate in the building and construction industry, or as an abrasive.

13.4.2 Performance

It is claimed by the proponent that the Plasma Waste Converter can be tailored to suit a specific application or waste type such as PCBs and hexachlorobenzene (HCB). It is claimed that the process has been in operation in Canada for eight years, however, no details of the specific applications or the performance achieved were provided.

Depending on the configuration of the unit, the Plasma Waste Converter may be particularly useful in treating PCB contaminated equipment, where the equipment itself is destroyed.

13.4.3 Considerations in the application of the Technology

All wastes can be treated, however, treatment of the gas stream produced by the Plasma Waste Converter will depend on the nature of the waste stream, and the end use of the gas.

13.4.4 Experience and Availability in Australia

The STARTECH Plasma Waste Converter is commercially available in Canada and the US, but has not yet been established in Australia. Zealmore Pty Ltd has been appointed as the agent for the technology in Australia. The technology has been approved by Canadian Authorities and is commercially available for all waste streams (Schallhammer, 1997)

13.4.5 Summary

(a) Proponents (In Australia)

Zealmore Pty Ltd

(b) Wastes Applicable

All waste types including solids, liquids, sludges and gases. No preconditioning or shredding is required.

(c) Contaminants Applicable

All scheduled compounds, solid or liquid.

(d) Status

The STARTECH system is not yet available in Australia, however, there is a demonstration unit in Ontario Canada and a commercial scale unit was commissioned in the US in 1996.

(e) Timing for Commercialisation in Australia

Available overseas now. Timing for implementation in Australia is market dependent and would be subject to the normal lead time for detailed design, construction and commissioning.

(f) Cost (example only)

The 400lb/hour (180kg/hr) unit cost approximately $1.6 million. Larger facilities are available up to 2000 ton/day (1815 tonne/day). The operating cost is approximately $375/ton ($413/tonne) but will depend on the waste stream being treated.

(g) Safety/Environmental Risk

The vitrified silicate slag is likely to exhibit low leachability with respect to metals. The system can be operated as a closed loop recycling system.

Care will be required during storage and handling of the Plasma Converted Gas (which may represent an explosion hazard) and during handling of the molten metal and slag produced by the process.

(h) Non-technical Impediments

Nil at this stage.

(i) Preferred Mode of Implementation

Centralised or relocatable unit.

(j) Limitations

To be determined.


1 Note that while CFCs and Halons are not classified as scheduled wastes, their treatment by the PLASCON technology is a further demonstration of the technology at a commercial scale and illustrates the potential for PLASCON to be applied in treating scheduled wastes in Australia.
Chapter 12 - Solvated Electron Technology Chapter 14 - Steam Detoxification