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.

We claim:  
     
         1 . A method of increasing fire resistance, erosion resistance, and corrosion resistance of a duct lined with a vacuum-formed ceramic fiber lining comprising treating said ceramic fiber lining with a coating, wherein said coating renders said duct capable of being used at temperatures from about 2300° F. to about 3000° F.  
     
     
         2 . A method according to  claim 1 , wherein said coating comprises a mixture of: silicon dioxide power; collodial silicon dioxide; water; and an emissivity agent.  
     
     
         3 . A method according to  claim 1 , wherein said coating comprises a mixture of: silicon dioxide power in an amount of from about 23.0 to about 44.0 wt %; collodial 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.  
     
     
         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 coaling 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 %; collodial 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 hex aboride, silicon tetraaboride, silicon carbide, molybdenum disilicide, tungsten disilicide and zirconium diboride.  
     
     
         7 . A method of making refractory lined ducts having an elongated, structurally supporting tube and a ceramic fiber liner carried on an interior wall of the duct comprising: 
 a) forming a sleeve and binder materials 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 duct to form an interference fit therewith effective in mechanically retaining said sleeve and duct 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.    
     
     
         8 . A method according to  claim 7 , wherein said sleeve is formed from a slurry of a material selected from the group consisting of mineral wool, graphite felt, ceramic fiber, and mixtures thereof.  
     
     
         9 . A method according to  claim 8 , wherein said slurry further comprises a material selected from the group consisting of plasticizing agents, de-wetting agents, and mixtures thereof.  
     
     
         10 . A method according to  claim 7 , further comprising treating said sleeve with a coating, wherein said coating comprises a mixture of: silicon dioxide power; collodial silicon dioxide; water; and an emissivity agent.  
     
     
         11 . A method according to  claim 7 , wherein said coating comprises a mixture of: silicon dioxide power in an amount of from about 23.0 to about 44.0 wt %; collodial 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.  
     
     
         12 . A method according to  claim 7 , wherein said sleeve is dried with microwave energy.  
     
     
         13 . A method according to  claim 7 , further comprising combining said duct with one or more of said ducts so as to make one complete duct.