Thermocouple For Stove Dome

Stove Dome & Brief process of Stove Dome

Stove is an important part of the iron making in Blast Furnace process and the temperature inside is above 1050°C.

The stove is first heated up by burninggas and combustion air within the chamber and allowing the heat to be absorbed into the refractory brick. When sufficient heat has been absorbed, the stove is put on-blast. In this mode, no combustion takes place, but cold blast air is forced through the stove and absorbs the heat to become hot blast. This is then mixed with cold blast to bring it to the right temperature, and is then forced into the blast furnace via the tuyeres which is the other section of this process.

It is quite common to have three stoves, so that at any time one stove is on-blast while the others are on-gas or boxed. A boxed stove has been heated up to temperature and sealed, so that it is ready to go on-blast. If one stove is down for repair, it is possible to run on just two stoves

Need of Temperature measurement in Stove Dome

Stoves run up to a maximum operating temperature of 1400°C as per the capacity. Combusted gas present inside the application has to be released steadily, with minimal energy loss. To withstand these pressure created by the gas, nowadays thermocouples are designed with high wall thickness to have a better resistance to thermal shock.

These thermocouples are installed on top of the Stove and are generally known as Stove Dome thermocouples.

Thermocouple Construction for this application

Element
For these applications Thermocouple types S / R are recommended with wire diameters of 0.50 or 0.45mm, in some applications for cost reduction ‘N’ type thermocouple can be used where the temperature is max 1100°C

Inner protection tube: 99.7% Recrystallized Alumina
Outer tube (Options)

Recrystallized Alumina 99.7% (Type: C-799) – High wall thickness (recommended) up to 1700°C
Recrystallized Silicon Carbide – Better thermal shock resistant up to 1500°C
Inconel 600 with ceramic coating – Better mechanical strength up to 1150°C

Glass Sealing: Glass sealing provides a pressure boundary, even if the bottom of the thermocouple breaks there shall be no leakage from the thermocouple head.

Holding tube: Inconel 600 or SS310 (As per process temperature)
Flange: Welded (recommended) or threaded (As per process requirement)
Head: Die cast aluminium, Ingress Protection IP67.