THE ASBESTOS CONVERSION PROCESS
A PERMANENT SOLUTION FOR THE ELIMINATION OF ACM (ASBESTOS CONTAINING MATERIAL) WASTE
Awareness and concern with the planet's environmental condition has brought about the obvious requirement to reverse the trend of unregulated air, water and land pollution. The previous fifteen years have witnessed responsible environmental policy in the developed countries. New technologies specifically intended for managing each waste stream promise to replace landfilling practices.
LANDFILLING AND THE ROLE OF NEW TECHNOLOGIES
As landfilling practices for the storage of regulated waste becomes less attractive or banned as is planned in France by the year 2002, the development of technologies such as the Asbestos Conversion System will be essential in providing alternative environmental treatment and disposal methods. In the United States many landfills are reaching capacity and U.S.EPA's halting of landfilling at sites failing regulatory storage practices continues to decrease the number of landfilling sites accepting ACM. Landfilling costs will continue to increase at an accelerating rate as fewer site are available and logistics problems drive up costs.
Regulatory agencies in the United States and Europe have placed highest priority on the policy of decreasing dependence upon landfilling while encouraging development of replacement technologies. In Holland the Environment ministry has recognized landfilling of hazardous waste as the worst available option and is considering all alternative methods. We are promoting the Asbestos Conversion process as the least expensive alternative .
The role of the new technologies is to responsibly and economically eliminate or recycle waste. Elimination of liability associated with landfills may be of only incidental concern to some generators or owners of asbestos waste today. But tomorrow the concern for stockpiled and landfilled waste will be magnified if historical results from landfill practice serve as any guideline. The Asbestos Conversion process is meant to break the liability chain forever, giving relief to the generator or owner of the ACM and for the regulatory authorities whose job it is to ensure that waste management methods provide for long-term public safety.
THE FUTURE OUTLOOK FOR SUCCESSFUL COMPANIES AND NEW TECHNOLOGIES So, what has been learned during previous experience with waste treatment technologies? Generally, those companies which have learned how to apply new waste management technologies in a timely manner while regulations were becoming tougher seem to be the same companies which are the economic survivors. Those companies unwilling or unable to adopt and utilize new waste technologies and which lag behind their proactive counterparts will be subject to increased production costs from ever higher disposal costs. Companies which thrive under the pressure of tighter regulatory control are those companies willing to learn how to practice new, more efficient waste management technologies soon after these technologies appear on the market. There is a lag time during the introduction of a new process during the lag, efficiency of use of the technology is increased. The lag time usually represents a valuable lull during which regulatory changes are occurring but not yet mandated. It is during this time that technology adaptations are usually least expensive and the latitude for practising a technology is greatest. I believe that implementation of the Asbestos Conversion process by companies in the demolition and asbestos abatement industries at this time will help position these pioneers in an extremely advantageous position during future years. The reward is the ability to practice a rather simple process which by its' very nature is very forgiving of real world problems of waste in homogeneities. The reward also is in establishing a waste management business based upon best available technology and the economic benefit for those who know and practice the process. THE ASBESTOS CONVERSION PROCESS: BEYOND THE DEVELOPMENT STAGE The process was developed by Asbestos Conversion Systems Inc. of Seattle and a pilot test plant was operated during 1987-1990. Patents were filed and after 4 years of testing all the approvals were eventually achieved in America in 1995 and the first commercial asbestos conversion unit was delivered at the end of that year to the Hanford Nuclear Reservation in the State of Washington. It is designed to process ACM at the rate of approximately 10 tonnes in 24 hours. It is operated by Bechtel Corp. on behalf of the Dept. of Energy.
The unit has now been in continuous operation for over a year. During this period, designs have been completed for new equipment having larger production capacities. Increased materials handling efficiencies have evolved in the same way as with most new processes.
Most important is the fact that the unit has been able to predictably convert ACM using a minimum of labour and expendables. And, the unit has produced good results even when moisture content soared as high as 65% by weight. In addition, a lot of the ACM contained an abnormally high content of plastic debris; up to 34% of feed weight; even so, exhaust data was well within regulatory boundaries. We are confident that a conversion plant of practically any size can be designed and safely operated anywhere in the world where minimum services are available.
ASCII PROCESS RECOGNITION AND EXPANSION OF APPLICATIONS
The U.S.EPA has granted permission to construct multiple facilities within the United States. Since the process destroys organic materials while converting asbestos minerals, great interest has also been shown in treating ACM which contains USEPA listed organic substances. Additionally, the process destroys PCBs and with an afterburner has been certified in America to process insulation materials co-contaminated with this hazard.
Radio nuclide contamination of ACM is another area of practical application of the process. Low processing temperatures, low exhaust emission volumes and the ability of the silicate systems in ACM to chemically bind radio nuclide sources are important considerations leading toward completion of pending agreements to use the process for radioactivity contaminated ACM at nuclear power plants and defence facilities.
SPECIAL REGULATORY CONSIDERATIONS
Asbestos abatement generates large volumes of potentially hazardous material which require safe disposal. At present, the only accepted disposal methods consist of landfilling or destroying the fibre mineral in the ACM by converting it to another physical form which is not characteristically fibrous. Regulatory agreement has been reached about the nature of fibre mineral conversion. ACM minerals which are "asbestos free" as indicated by detection of no asbestos minerals by TEM analysis are considered to be solid waste and are no longer regulated as asbestos waste. In the United States for example, there is no de minims value for "asbestos free" minerals and therefore the converted ACM cannot contain any trace of asbestos minerals. This level of process performance at non-detection limits is well within the limit of demonstrated performance by the Asbestos Conversion Systems Process and probably few others.
THE TECHNOLOGY I: ASBESTOS CONVERSION - HOW IT WORKS
Asbestos fibres degrade slowly in high temperature environments. For this reason, asbestos has found so many uses in high temperature insulations. The target of the ACSI investigation was to find a method to drastically reduce mineral conversion temperature and time in order to make the process economically feasible.
Other conversion processes which rely on only very high operating temperatures to convert asbestos fibres stretch the limits of equipment operating temperatures, require high energy input, and generally have heavy maintenance upkeep.
ACM may also be used to form a glass. However, it is difficult to formulate a glass batch which will universally match all ACM chemistries. Instead, the vitrification approach usually leads to the addition of relatively large amounts of glass formers and fluxes to successfully overcome variable ACM chemistries. Vitrification in conventional fuel fired or all-electric glass furnaces also has the obvious disadvantage of not dealing with the metals contamination problem. Metal sorting is not practical.
During 1987 ACSI discovered that asbestos fibre minerals could be converted to harmless non-fibrous, crystalline minerals at temperatures substantially below those usually required to induce conversion. Conversion occurred at lower temperatures and also in much shorter times. Considerable scientific investigation revealed the thermodynamic and chemical demineralization mechanisms that converted the fibres to crystals, thus rendering the asbestos inert. The choice of demineralizing agent proved to be very important in causing conversion at lowest temperatures and in shortest times. Boron additives proved best suited. These, together with wetting agents are non-toxic and require no special handling by personnel.
New technologies often seem to suffer from the same shortcomings: The equipment required to enable the new technology to work properly has not yet been invented! In terms of the ACSI process design, demineralization processing methods meant that readily available equipment which operates at moderate temperatures, between 1100 & 1200°C, could be used. A demineraliser which worked over short time periods was another major benefit. Samples of asbestos fibre furnace components which might have a service lifetime of one to two years were noted to degrade in less than one hour at the same industrial service temperature conditions when coated with the demineralising agent. The process uses a demineralizing agent which is unaffected by the presence of organic and inorganic materials. The amount of agent added typically is 2-4% of the ACM weight and applied to the ACM in an aqueous form, consistent with ACM wetting for purposes of dust suppression.
THE TECHNOLOGY II: REAL WORLD PROBLEMS
In the real world of ACM processing, one finds that human beings have mixed countless industrial chemicals, cements, clays, fillers, organic and inorganic coatings with ACM. During ACM abatement, the situation is compounded as building material fragments, disposables used in abatement, metal objects and garbage are packed into abatement bags. Water content of ACM can and does vary tremendously.
As a result of the forgiving nature of the ACSI process, sorting of extraneous materials is not necessary. Thermal cycling destroys organic components, yielding water and salt solutions from acid gas exhaust polishing. Particularly bothersome chemical agents such as PCBs and VOC compounds are destroyed. Tramp metal enters and exits the process with little change; melting of some non-ferrous materials occurs without any consequence. It is not uncommon to encounter paints or coatings on ACM which contain toxic metal compounds. Lead, copper, cadmium, chromium, and zinc are the most common toxic metals constituents. During the thermal cycling of ACM in the ACSI process the toxic metals are chemically bound and become unavailable as tested by the USEPA Toxic Characteristic Leach Procedure.
The all-important attribute of the ACSI process is that it works regardless of the makeup of the ACM. It converts the asbestos content to non-detectable levels of asbestos minerals without fail. Not sometimes, but always.
THE TECHNOLOGY III: PROCESS DESCRIPTION
The hardware comprises a materials handling system, shredder, mixing bath, dewatering screw, rotary hearth and quench tank. All this can be mounted in a large trailer enabling the process to be undertaken at site in the case of very large asbestos removal contracts, or set up in a central location by perhaps the municipality or even a current landfill operator. The whole process is controlled by computer and does not, therefore, require ANY dedicated labour to operate. The asbestos containing waste is loaded into the machinery either manually or by vacuuming directly into hoppers which will automatically feed into the system. The waste then passes through a shredder, into the chemical bath, then via the dewatering screw (to remove excess moisture) to the furnace. It is preheated to remove the rest of the moisture and then passes on to the rotary hearth where it is heated to 1200 degrees centigrade for one hour before being ejected into the quench tank and from there into a sealed skip.
THE TECHNOLOGY IV: REGULATORY ATTRIBUTES
Batch Analysis, Certificate of Destruction
The ACSI process converts asbestos fibres in ACM to non-detectable levels as determined by TEM analysis. Each batch is analysed and a Certificate of Destruction issued. There is a considerable reduction in volume, up to eight times reduction for sprayed flock. Exhaust Emission Exhaust emission from the thermal processing unit is well below the USEPA threshold clearance level of 0.010 fibres/ml. Air samples taken from outside the regulated area are also well within threshold clearance levels. Even samples taken inside the processing trailer exhibit results well below occupational exposure limits. Measurements of exhaust emission show low carbon dioxide emissions. The ACSI process operates with exhaust temperature and dwell time well in excess of USEPA's 2 second burn time at 1200°C required for destroying organic compounds. Complete combustion is assured by addition of up to 100% excess air in the afterburner section of the thermal converter. Fast cooling of the exhaust fumes ensures no Dioxins are formed.
Cooling water for furnace components, washdown and personnel showers is recycled internally and used as makeup water for the demineralization solution, exhaust quench, etc.
Converted ACM meets all aquatic bioassay tests. Converted ACM does not readily degrade by weathering and is a non-dusty product consisting of hard rocklike mineral lumps. Because of its sizing, it can be used as hard-core and road base etc. Potential Recycling of Converted Material Since the converted material contains high levels of calcium, magnesium and iron, a granular product might be useful as a supplement in agricultural amendments for soil conditioning.
Electricity is consumed at the rate of 300 - 350 Kilowatt Hours per Tonne according to the level of water content. The total conversion cost is under $300 per tonne.