Thermocouple for use in a hostile environment

Claim 1

In a temperature monitoring system for a reactor having a refractory lined wall which defines a combustion chamber in which a carbonaceous fuel is gasified at a high temperature to produce a usable gas, and a residual slag comprising an amount of free metal therein, said combustion chamber refractory lined wall including means forming an access passage (16) with an opening at the combustion chamber, a multi-segment thermowell (32) removably registered in said access passage (16) defining an annulus (38) therewith, having a closed end wall (36) disposed contiguous with the combustion chamber wall, and an open end, said thermowell (32 being comprised of discrete first (33), and second (34) cylindrical segments, each thereof being formed of a different refractory material, means forming a removable, gas tight closure (22) at said refractory lined wall adjacent the thermowell open end, a thermocouplee (24) removably received in said thermowell and having thermocouple wires (26) and (27) which pass through said gas tight closure (22), and a gas conduit means (39) communicated with a pressurized source (41) of purge gas and opening into said thermowell (32) to envelop said thermocouple (24) with a flow of purge gas which exits into said combustion chamber (12).