Vitrification of asbestos waste

• US 4,678,493 A
• Filed: 08/25/1986
• Issued: 07/07/1987
• Est. Priority Date: 11/21/1983
• Status: Expired due to Fees

• Current Assignee: King Taudevin & Gregson Limited
• Original Assignee: King Taudevin & Gregson Limited
• Inventors: Johnson, Henry S., Roberts, David
• Primary Examiner(s): Lindsay, Jr., Robert
• Application Number:
  US06/899,630
• Time in Patent Office: 316 Days
• Field of Search: 501/27, 501/30, 501/32, 501/155, 65/27, 65/134, 65/346, 65/347, 65/339, 65/342, 252/629
• US Class Current: 588/254
• 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

Waste 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; 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 vitreous glass product which comprising the steps of:

providing an electrical glass melting furnace having two regions, a first region of said regions defining a closed melting chamber including means for feeding asbestos into the melting chamber and means for permitting the molten glass melt formed in said melting chamber to flow from said first region to a second region in said furnace comprising means in said furnace located between said first region and said second region for separating the furnace into said two regions capable of containing molten glass at a temperature of at least 1000°

C., said two regions communicating with each other below the level of said melt;

supplying asbestos and a source of glass into said first region of said furnace;

heating said asbestos and said source of glass to form a melt;

maintaining said melt at less than atmospheric pressure, and a temperature of at least 1000°

C. for a sufficient period of time to decompose the asbestos;

withdrawing the melt from said second region of the furnace at a preselected temperature of at least 1000°

C. by permitting the melt to continuously flow from said first region maintained at a reduced pressure to said second region from which it is withdrawn by discharge from the said second region at atmospheric pressure;

said flow between said first and second regions being confined to flow of the melt below the surface of the melt, whereby during continuous operation of said process the restricted flow of said melt between the two regions of said furnace can occur while maintaining less than atmospheric pressure above said first region and while withdrawing a homogeneous melt from said second region containing substantially no undecomposed asbestos.

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

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

4. A process according to claim 2, wherein the asbestos is fed into the furnace by sealed mixing and conveying means.

5. A process according to claim 4 wherein an asbestos waste hopper and a cullet or glass-making materials hopper feed into a screw conveyor leading to the furnace.

6. A process according to claims 2, wherein the material supplied to the furnace further comprises a melt accelerator.

7. A process according to claim 6 wherein the melt accelerator is an alkali metal compound, an alkaline earth metal compound, a boron compound, a flouride or chloride or a blast furnace slag.

8. A process according to claim 7, wherein the melt accelerator comprises sodium hydroxide.

9. A process according to claim 8, wherein the material fed to the glass melting furnace comprises 20-80%, by weight asbestos, 80-20% cullet and 0.5-5% sodium hydroxide.

10. A process according to claim 1, wherein the furnace is maintained at a temperature of 1350°

-1380°

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

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