Furnace and a Method for Cooling a Furnace

Abstract

A furnace for conducting a high temperature process under oxidising conditions comprises an outer shell made from a metal, one or more cooling channels formed on or joined to the outer shell and a furnace lining. The furnace lining comprises a backing lining comprising a relatively high thermal conductivity layer positioned adjacent to an inner wall of the outer shell and a working lining positioned inwardly of the layer of relatively high thermal conductivity. The backing lining can comprise a graphite lining or a graphite-containing lining. The rate of heat transfer through the backing lining is sufficiently high to form a protective freeze on the backing lining in the event that the working lining wears away.

1 .- 12 . (canceled) 
     
     
         13 . A method for cooling a furnace in which a high temperature process is conducted under oxidising conditions, the method comprising providing a furnace comprising an outer shell made from a metal, one or more cooling channels formed on or joined to an outer surface of the outer shell and a furnace lining, the furnace lining comprising a relatively high thermal conductivity backing lining positioned adjacent to an inner wall of the outer shell, the backing lining comprising graphite tiles or graphite bricks or tiles or bricks made from a material including graphite or tiles or bricks made from a carbon-based material, and a refractory working lining positioned inwardly of the backing lining, the backing lining having a thermal conductivity that is significantly higher than the thermal conductivity of the refractory working lining, the backing layer having a thermal conductivity that is similar to or higher than the thermal conductivity of the outer shell, operating the process in the furnace and passing cooling water through the cooling channels to cool the furnace such that the maximum temperature reached in the backing lining does not exceed 500° C. 
     
     
         14 . A method as claimed in  claim 13  wherein the process is operated with a partial pressure of oxygen in the furnace atmosphere of greater than 10 −9  atm. 
     
     
         15 . A method as claimed in  claim 13  wherein the backing lining has a thermal conductivity that is about three to four time higher than the thermal conductivity of the outer steel shell. 
     
     
         16 .- 17 . (canceled) 
     
     
         18 . A method as claimed in  claim 13  wherein the maximum temperature reached in the graphite layer or the layer of a material of or including graphite or the layer of a carbon-based material does not exceed 400 ° C.. 
     
     
         19 . A method as claimed in  claim 13  wherein heat is removed from the furnace at a rate of 5 kW/m 2  under normal operating conditions and a new working lining, up to 25 kW/m 2  for a worn working lining, and not exceeding a localised heat flux of 120 kW/m 2  under extreme operating conditions and localized failure of the working lining. 
     
     
         20 . A method as claimed in  claim 13  wherein cooling water flows through the cooling channels at an average rate of 1 to 2 m 3 /h per m 2  of furnace shell area, and at a minimum velocity in the cooling channels of 1 m/s. 
     
     
         21 . A method as claimed in  claim 13  wherein a temperature of the outer surface of the outer steel shell of the furnace falls in the range of from 40 to 80 ° C. 
     
     
         22 . A method as claimed in  claim 13  wherein the rate of cooling of the backing lining is sufficiently high such that in the event that the working lining becomes completely worn away in a part of the furnace a protective and stable freeze layer will form on the backing lining to protect the backing lining from being oxidised. 
     
     
         23 . A method as claimed in  claim 13  wherein the furnace is operated for a period of time under oxidising conditions and is operated for a brief time under reducing conditions. 
     
     
         24 . (canceled) 
     
     
         25 . A method as claimed in  claim 13  wherein the graphite bricks or tiles or bricks or tiles made from a material including graphite or tiles or bricks made from a carbon-based material have the thickness of between 30 and 250 mm. 
     
     
         26 . A method as claimed in  claim 13  wherein the graphite bricks or tiles or bricks or tiles made from a material including graphite or tiles or bricks made from a carbon-based material have the thickness of between 50 and 100 mm. 
     
     
         27 . A method as claimed in  claim 13  wherein the graphite bricks or tiles or bricks or tiles made from a material including graphite or tiles or bricks made from a carbon-based material have the thickness of approximately 70 mm. 
     
     
         28 . A method as claimed in  claim 13  wherein the maximum temperature reached in the graphite layer or the layer of a material of or including graphite or the layer of a carbon-based material does not exceed 250° C. 
     
     
         29 . A method as claimed in  claim 13  wherein cooling water flows through the cooling channels at an average rate of 1 to 2 m 3 /h per m 2  of furnace shell area, and at a minimum velocity in the cooling channels of above 2 m/s.