Thermocouple for use in gasification process

Abstract

An improved apparatus comprising a thermocouple for measuring the temperature in a gasification process is provided. The improvement comprises a sapphire envelope for enclosing at least a portion of the thermocouple. The sapphire envelope may be in the form of a sapphire sheath fitted over the thermocouple. The apparatus may also comprise a thermowell, with the sapphire envelope being provided by the thermowell.

What is claimed is:  
     
         1 . In an apparatus comprising a thermocouple for measuring the temperature in a gasification process, the improvement comprising a sapphire envelope for enclosing at least a portion of said thermocouple.  
     
     
         2 . The apparatus of    claim 1   , said thermocouple comprising a pair of wires of dissimilar metal content joined together at one end by a hot junction and at the other end by a cold junction but otherwise electrically insulated from each other by an insulating tube, wherein the sapphire envelope is in the form of a sapphire sheath having a closed distal end and an open end, said open end having been fitted over the hot junction and at least a portion of the insulating tube.  
     
     
         3 . The apparatus of    claim 1   , further comprising a thermowell, said thermowell surrounding said thermocouple and said thermowell comprising at least one barrier layer comprised of sapphire.  
     
     
         4 . The apparatus of    claim 1   , further comprising a thermowell, said thermowell surrounding said thermocouple and said thermowell comprising an inner protection tube and an outer protection tube, said inner protection tube comprised of sapphire, wherein said sapphire envelope comprises said inner protection tube.  
     
     
         5 . The apparatus of    claim 2   , further comprising a thermowell, wherein the gasification process employs as a reactor a vertical free-flowing refractory lined cylindrical steel pressure vessel, and wherein the thermocouple fitted in the sapphire sheath is installed in the gasification reactor by being passed in succession straight through a flanged reducer and into the thermowell connected to the flanged reducer, the thermowell being installed in the gasification reactor by first passing it through a hole in the steel wall of the pressure vessel and by then passing it through an aligned hole in the refractory lining the wall on the inside of the pressure vessel.  
     
     
         6 . The apparatus of    claim 2   , further comprising a thermowell, said thermowell surrounding said thermocouple and said thermowell comprising an inner protection tube and an outer protection tube.  
     
     
         7 . The apparatus of    claim 6   , wherein the inner protection tube is comprised of aluminum.  
     
     
         8 . The apparatus of    claim 6   , wherein the inner protection tube is comprised of sapphire.  
     
     
         9 . The apparatus of    claim 1   , wherein the thermocouple is under the ambient pressure of the gasification process.  
     
     
         10 . The apparatus of    claim 1   , wherein the temperatures to be measured range from about 1,700° F. to about 3,000° F.  
     
     
         11 . The apparatus of    claim 2   , wherein the pair of wires are comprised of platinum, rhodium, or mixtures thereof.  
     
     
         12 . The apparatus of    claim 2   , wherein the insulating tube is comprised of alumina.  
     
     
         13 . The apparatus of    claim 2   , wherein the insulating tube is comprised of sapphire.  
     
     
         14 . In an apparatus for measuring the temperature in a gasification process, said gasification process employing a reactor comprising a vertical free-flow refractory lined pressure vessel, said apparatus comprising a thermowell and one or more thermocouples, said one or more thermocouples independently comprising a pair of wires of dissimilar metal content joined together at one end by a hot junction and at the other end by a cold junction but otherwise electrically insulated from each other by an insulating tube; the improvement comprising a sapphire envelope for enclosing at least a portion of at least one thermocouple.  
     
     
         15 . The apparatus of    claim 14   , wherein the sapphire envelope is in the form of a sapphire sheath having a closed distal end and an open end, said open end having been fitted over the hot junction and at least a portion of the insulating tube of the thermocouple.  
     
     
         16 . The apparatus of    claim 14   , wherein said thermowell comprises at least one barrier layer comprised of sapphire, wherein said sapphire envelope comprises the at least one barrier layer comprised of sapphire.  
     
     
         17 . The apparatus of    claim 14   , wherein said thermowell comprises an inner protection tube and an outer protection tube, said inner protection tube comprised of sapphire, wherein said sapphire envelope comprises said inner protection tube.  
     
     
         18 . The apparatus of    claim 14   , said thermowell being installed in the reactor by first passing it through a hole in the steel wall of the pressure vessel and by then passing it through an aligned hole in the refractory lining the wall on the inside of the pressure vessel, the one or more thermocouples being installed in the reactor by passing the thermocouples in succession straight through a flanged reducer and into the thermowell connected to the flanged reducer.  
     
     
         19 . The apparatus of    claim 15   , said thermowell surrounding said thermocouple and said thermowell comprising an inner protection tube and an outer protection tube.  
     
     
         20 . The apparatus of    claim 19   , wherein the inner protection tube is comprised of alumina.  
     
     
         21 . The apparatus of    claim 19   , wherein the inner protective tube is comprised of sapphire.  
     
     
         22 . The apparatus of    claim 14   , said thermowell having one or more inner protection tubes, wherein the number of inner protection tubes is at least equivalent to the number of thermocouples, and wherein the distal ends of the one or more protection tubes are positioned at different points along the length of the thermowell.  
     
     
         23 . The apparatus of    claim 14   , wherein the one or more thermocouples are under ambient pressure of the gasification process.  
     
     
         24 . The apparatus of    claim 14   , wherein the temperatures to be measured range from about 1,300° F. to about 3,000° F.  
     
     
         25 . The apparatus of    claim 14   , wherein the pair of wires are comprised of platinum rhodium, or mixtures thereof.  
     
     
         26 . The apparatus of    claim 14   , wherein the insulating tube is comprised of alumina.  
     
     
         27 . The apparatus of    claim 14   , wherein the insulating tube is comprised of sapphire.  
     
     
         28 . A thermocouple comprising a pair of wires of dissimilar metal content joined together at one end by a hot junction and at the other end by a cold junction but otherwise electrically insulated from each other by an insulating tube, the thermocouple further comprising a sapphire sheath having a closed distal end and an open end, said open end having been fitted over the hot junction and at least a portion of the insulating tube.