Refractory lined ducts and coating for use therewith

Abstract

The present invention is directed to ceramic fiber insulation and related products and methods. A coating that is capable of being brushed and/or sprayed lightly as a liquid onto vacuum-formed ceramic fiber insulation for use at high temperatures is also provided.

1 - 3 . (canceled)  
   
   
       4 . A ceramic fiber lined duct comprising a vacuum-formed ceramic fiber liner that has been treated with a coating affixed to a metal jacket.  
   
   
       5 . A vacuum-formed ceramic fiber lined duct according to  claim 4 , wherein said coating comprises a mixture of: silicon dioxide power; collodial silicon dioxide; water; and an emissivity agent.  
   
   
       6 . A vacuum-formed ceramic fiber lined duct according to  claim 4 , wherein said coating comprises a mixture of: silicon dioxide power in an amount of from about 23.0 to about 44.0 wt %; colloidal silicon dioxide in an amount from about 25.0 to about 45.0 wt %; water in an amount from about 19.0 to about 39.0 wt %; and an emissivity agent selected from the group consisitng of silicon hexaboride, silicon tetraaboride, silicon carbide, molybdenum disilicide, tungsten disilicide and zirconium diboride.  
   
   
       7 - 13 . (canceled)  
   
   
       14 . A refractory lined duct comprising an elongated, structurally supporting tube and a liner carried on an interior wall of the duct prepared by the process comprising: 
 a) forming a sleeve on a structurally supportive die in a hydrated state by vacuum-forming wherein said sleeve has an external wall of a configuration that is geometrically and dimensionally complemental to the interior wall of the supporting tube to form an interference fit therewith effective in mechanically retaining said sleeve and tube in fixed interengagement;    b) inserting the sleeve, while in a hydrated state and on the die, coaxially into the supporting tube and after insertion, removing the die from the sleeve; and    c) drying the sleeve while said sleeve is maintained in fixed position within the supporting tube to remove substantially all liquid resulting in solidification of the sleeve in a frictionally and adhesively retained relationship with the supporting tube;    wherein said method further comprises treating said sleeve with a coating, wherein said coating comprises a mixture of: silicon dioxide powder; collodial silicon dioxide; water; and an emissivity agent.