Vitrification of asbestos waste

• US 4,820,328 A
• Filed: 07/02/1987
• Issued: 04/11/1989
• Est. Priority Date: 11/21/1983
• Status: Expired due to Fees

• Current Assignee: King Taudevin & Gregson Limited
• Original Assignee: King Taudevin & Gregson Limited
• Inventors: Roberts, David, Stuart, Johnson H.
• Primary Examiner(s): Lindsay, Robert L.
• Application Number:
  US07/069,179
• Time in Patent Office: 649 Days
• Field of Search: 501/27, 501/30, 501/32, 501/155, 65/27, 65/134, 65/346, 65/347, 65/339, 65/342
• US Class Current: 65/134.3
• CPC Class Codes: A62D 2101/41 Inorganic fibres, e.g. asbestos
• CPC Class Codes: A62D 3/40 by heating to effect chemical change, e.g. pyrolysis
• CPC Class Codes: B09B 3/0066 Disposal of asbestos
• CPC Class Codes: B09B 3/40 involving thermal treatment, e.g. evaporation processes using mineral binders involving a melting or softening step B09B3/29; involving radiation B09B3/50
• CPC Class Codes: C03B 19/1045 by bringing hot glass in contact with a liquid, e.g. shattering
• CPC Class Codes: C03B 19/109 Glass-melting furnaces specially adapted for making beads
• CPC Class Codes: C03B 5/005 of glass-forming waste materials disposal or transformation of solid waste in general B09B; treatment of radioactive waste G21F9/00
• CPC Class Codes: C03C 1/002 Use of waste materials, e.g. slags
• CPC Class Codes: Y02P 40/50 Glass production, e.g. reusing waste heat during processing or shaping

Abstract

Wate asbestos is converted into a glass by maintaining within an electrical glass melting furnace a body of molten glass at a temperature above the decomposition temperature of asbestos; supplying asbestos to the furnace by a conveyor discharging above the body of molten glass so that the asbestos falls onto the molten glass and becomes decomposed and melted into glass; and withdrawing molten glass from the furnace at a temperature of at least 1000° C. The asbestos is advantageously mixed with cullet and a melt accelerator and fed into the furnace by means of a screw mixer/conveyor. The furnace is advantageously operated at a pressure less than atmospheric pressure.

Claims

1. A process for converting waste asbestos into a glass which comprises:

heating within an electrical glass melting furnace a body of molten glass so as to maintain said body of molten glass at a temperature above the decomposition temperature of asbestos;

supplying asbestos to the furnace by conveyor means discharging above the body of molten glass so that the asbestos falls onto the molten glass and becomes decomposed and is melted to glass, the asbestos that has fallen onto the molten glass being subjected for a sufficient period to a temperature above its decomposition temperature that it is completely melted and becomes part of the body of molten glass and the asbestos being supplied in an amount such that a substantial proportion of the molten glass in said body is derived therefrom, wherein said conveyor means discharges the asbestos into a melting chamber containing partition means contacting the body of molten glass and defining a submerged throat in said furnace; and

withdrawing molten glass from the furnace at a temperature of at least 1000°

C.

3. The process of claim 1, wherein the glass in the melting chamber is heated by means of electrode means in the body of molten glass and by radiant heater means disposed above the body of molten glass.

4. The process of claim 3, wherein the glass passes from said throat by riser means to forehearth means, means in said forehearth means defining a bottom opening through which molten glass is discharged.

5. The process of claim 4, wherein the forehearth is heated by second radiant heater means disposed above the molten glass.

6. A process according to claim 1, wherein the asbestos is mixed with cullet before it is fed into the furnace.

7. A process according to claim 1, wherein the asbestos is mixed with glass-making materials before it is fed into the furnace.

8. A process according to claim 6, wherein the asbestos is fed into the furnace by sealed mixing and conveying means.

9. A process according to claim 8, wherein an asbestos waste hopper and a cullet or glass-making materials hopper feed into a screw conveyor leading to the furnace.

10. A process according to claim 6, wherein the material supplied to the furnace further comprises a melt accelerator.

11. A process according to claim 10, wherein the melt accelerator is selected from the group consisting of alkali metal compounds, alkaline earth metal compounds, boron compounds, or chlorides or blast furnace slag.

12. A process according to claim 11, wherein the melt accelerator comprises sodium hydroxide.

13. A process according to claim 12, wherein the material fed to the glass melting furnace comprises 20-80%, by weight asbestos, 80-20% cullet and 0.5-5% sodium hydroxide.

14. A process according to claim 1, wherein the furnace is maintained at a temperature of more than 1250°

C. and the residence time of the asbestos is at least 1 hour.

15. A process according to claim 1, wherein a stream of glass discharged from the furnace is quenched by passage into a bath of water.

2. In a process for converting waste asbestos into a glass by feeding asbestos into a closed melting chamber of an electrical glass melting furnace by conveyor means discharging above the body of molten glass so that the asbestos falls onto the molten glass becomes dissolved and is melted to glass with the asbestos being supplied in such amount that a substantial proportion of the molten glass is derived therefrom, flowing said glass to forehearth means by partition means depending from a roof of said furnace into the body of molten glass to define a submerged throat for said furnace and riser means leading from said throat to said forehearth means, and discharging the molten glass through an orifice in the forehearth means, preventing premature crystallisation of materials present in the melt on contact with the surfaces of said throat, riser, forehearth and orifice by maintaining the temperature of the molten glass above 1100°

C. until the glass is discharged through the orifice.