| 1. | Process for recycling of asbestoscontaining hazardous wastes, involving compacting of wastes (in powder or lumpy form) with addition of auxiliary materials and melting at a temperature of 12001600 °C and at overpressure of 00, 07 MPa to a glasslike endproduct suitable for direct use, as a raw material, in glass production. |
| 2. | The process in Claim 1. characterised by a melting process performed in a continuous or discontinuous (batchtype) equipment. |
| 3. | Claim 1. characterised by the physical preparation (milling) of the wastes available in the form of powder or lumps and the dustcontaining or pulverised wastes are pelleted with addition of Na2C03 and water. |
| 4. | Claim 3. characterised by obtaining a lumpy form via pelletisation. |
| 5. | Claim 1. characterised by the fact, that glassfilament can be drawn from the glassEke melt. AMENDED CLAIMS [received by the International Bureau on 12 September 2001 (12.09.01); original claims 15 replaced by new claims 15 (1 page)] 1. Procedure for the recycling of asbestos containing hazardous waste, characterised by the following: in the course of treatment, the asbestos containing ground waste compacted into granules of range of 5 to 20 mm using the aqueous solution of Na2C03 in a proportion of 15% as compared to the mass of the waste, by adding Na2CO3 producing solidity required for feeding, is intermittently or continuously fed to the glass furnace heated by mineral energy sources up to a temperature of 1200 to 1600°C, in the course of feeding, the quantity of asbestos containing substance compared to the whole fed quantity is 10 to 70 m/m%, other substances are added to the asbestos containing substance in the following composition compared to the whole mass of the mixture : Sand (Si02) 2545% Dolomite (MgCaC03) 010% AL203carrier (e. g. feldspar) 010% Gypsum (CaS04) 0.10. 5% Soda (Na2C03) 315% Scrap glass 040% 2. Procedure according to patent claim No. 1 characterised by preparation and melting in equipment of intermittent or continuous operation. |
| 6. | 3 Procedure according to patent claims Nos. l or 2 characterised by physically preparing coarse waste and agglomerating powdered or powder waste by adding binding material and water. |
| 7. | 4 Procedure according to any of patent claims Nos. 1 to 3 characterised by drawing glass fibre out of the melt. |
| 8. | 5 Procedure according to any of patent claims Nos. 1 to 4 characterised by letting the product resulting from the procedure out of the equipment for further utilisation. |
The asbestos are fibrous calcium and/or calcium-magnesium-silicates of mineral origin. Owing the low thermal conduction capabilities and therefore its heat- resistance resulting from the fibrous structure asbestos was incorporated into equipment operating at high temperatures and used in various forms in the building-construction and mechanical engineering sectors.
Although nowadays new applications of asbestos are not permitted in our country the processing industry specialising its operation on asbestos is still in operation.
Asbestos-containing hazardous wastes are generated therefore primarily by demolishing obsolete instalments. These can appear mostly in a dust-like or coarse lumpy form of hazardous wastes.
Very few generally accepted processes are available for processing of hazardous wastes with asbestos content. Waste generated are displaced mostly in hazardous waste disposal sites. This is the most widely employed process in Hungary as well.
A different group of solutions are comprising pre-treatment of asbestos- containing hazardous wastes whereby the product generated after pre-treatment can be disposed off in any type of a disposal site. Within the range of these processes certain approaches aim at recycling/of the hazardous waste. These approaches are employed for elimination the fibrous structure of the asbestos.
One common feature of these latter solutions is shattering/destroying the asbestos filaments via combustion and/or melting in a closed system at high temperature.
The product generated by this process-in any case-will have to have a hazard rating lower then that of the original waste. Patent Specification No. HU 205 333 A is describing a process for making use in building-construction of a waste containing a concrete-asbestos mixture, provided certain conditions are met.
With this process the fibrous structure of the asbestos is not eliminated and upon a subsequent demolishment hazardous wastes are generated again. Patent Specification No. HU 214 374 B describes a process for blending asbestos- containing hazardous waste into the usual raw materials used for making bricks to be followed by firing of the bricks. The fibrous structure is not eliminated in with this procedure either and asbestos fibres are emitted into the environment upon demolishing of the building constructed from such bricks. Building-constructional use is intended by European Patent EP 0,548,850A1 as well describing a process for blending the asbestos-containing wastes with the usual building-constructional raw materials following their treatment with inorganic acids having a certain fluorine content. Fluorine itself, being a highly aggressive compound, can pose a hazard when it is emitted as an air polluting agent into the environment. The process claimed by Patent US 5,188649 involves vitrification of the asbestos- containing hazardous wastes between electrodes and utilisation of the glass-like melt as a filler-following rapid cooling-in road construction. Although this procedure is suitable for destruction/shattering of the fibrous structure, the high process costs and the limited range of applications make this process less attractive. In France with the process published in the Revue de l'Electricité et de l'Electronique (1995, Volume 3/September, pp.: 37-40) asbestos wastes are melted with the aid of a plasma-burner, the resulting product is either used as a filler in road construction, used in applications similar to those in the case of boiler slag or dumped at waste disposal sites.
The scope of the invention is the conversion of asbestos-containing hazardous wastes (dusts or lumps) and direct usage in the production of glass.
The invention is a process for recycling/recycling of hazardous wastes with asbestos content. The process involves compacting of the milled asbestos- containing wastes with auxiliary materials, continuous or discontinuous melting of same into a pre-glass condition at a temperature and pressure of 1200-1600 oC and 0,0,07 MPa respectively, and solidifying the glass drained by gravitation with direct water jet cooling. Raw-and auxiliary material requirements are as follows: -Raw materials: sand (Si02) dolomite (MgCaCO3) A1203-carrier (such as feldspar) shredded glass -Auxiliary materials: gypsum (CaS04) caustic soda (Na2CO3) Based on results of actual measurements the end-product, obtained from asbestos-containing wastes having known oxide contents and after adjustment of the composition with the addition of auxiliary materials, suitable for direct use in glass production with the resulting additional advantage of reduced raw material consumption and energy saving.
The advantage offered by the process is, that instead of products considered up to now unsuitable for use (land filled, blended into concrete) or a product used on a single occasion (such as"fillers"in road construction) results in a product (glass) which can be repeatedly recycled.
Another great advantage of the process is, that notwithstanding the composition of or the extent hazard represented by the asbestos-containing waste, with the addition of specific amounts of auxiliary materials compositions of the glass obtained can be varied according to requirements.
Example 1 300 g asbestos sample of known composition is mixed with raw-and auxiliary materials the amounts of which are dependent on the desired composition of the glass produced.
Asbestos composition: sio2 = 7, 17 m/m % A1203 = 2, 53 m/m % Cas 47, 63 n/m % MgO = 2, 18 m/m % Na20-3, 11 m/m % ignition loss = 37, 38 m/m% Quantities of raw-and auxiliary materials added: sand = 280 g caustic soda = 40 g gypsum = 2 g dolomite = 40 g feldspar = 0 g glass pieces = 200 g The asbestos-containing waste is milled in an aqueous suspension, mixed with 70 % of the calculated amount of the caustic soda and pelletised. The tablets are mixed with the specified amount of raw materials. After wetting to 5 % water content for dissolving a part of the caustic contained in the mixture, the mixture is placed in a porcelain crucible. The crucible's contents are melted over 6 hours at a temperature of 1200 °C in an electric resistance-furnace at atmospheric pressure. At the end of the specified length of time the total amount of the mixture melts to a glass-like state which, in addition to permitting drawing from it a glass- filament, is having a composition suitable for use directly in the production of glass.
Example 2.
The procedure is similar to that described in Example 1. above with the exception of the composition of the asbestos used, requiring addition of different amounts of raw-and auxiliary materials. Melting temperature applied is 1500 °C.
Quantity of asbestos-containing waste: Si02 = 31, 50 m/m % Cas 35,, 06 m/m % MgO = 6, 55 m/m % ignition loss = 26, 89 m/m% Quantities of raw-and auxiliary materials added: sand = 200 g caustic soda = 40 g gypsum = 2 g dolomite = 45 g feldspar = 10 g glass pieces = 200 g Composition of the resulting product is similar to that in Example 1. above, permitting both its utilisation in glass production and drawing of glass filaments.
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