Measuring very high dome temperature in a blast-furnace hot-blast stove Which instrument provides the most accurate, reliable indication at the stove dome, where temperatures are extremely high and direct contact is impractical?

Introduction / Context:
Blast-furnace stoves (hot-blast stoves) operate with dome temperatures that can exceed 1000°C. Selecting the right temperature instrument is critical because extreme heat, combustion gases, and radiant energy make many contact sensors inaccurate or short-lived. This question checks your understanding of non-contact high-temperature measurement principles.

Given Data / Assumptions:

• Measurement location: stove dome of a blast-furnace hot-blast stove.
• Very high temperatures (well above typical contact sensor comfort zones).
• Goal: maximize accuracy and reliability without direct immersion.

Concept / Approach:
Radiation (optical) pyrometers determine temperature from the thermal radiation emitted by a hot surface according to radiation laws. Because they are non-contact, they avoid problems like sensor drift due to oxidation, sheath failure, and conduction errors. Thermocouples can measure high temperatures, but survivability and reference errors increase in harsh, radiative environments. Resistance thermometers (e.g., platinum RTDs) are excellent at moderate temperatures but are unsuitable at such high values.

Step-by-Step Solution:

Verification / Alternative check:
Plant practice often uses optical/radiation pyrometers for stove domes and molten streams. When emissivity is accounted for and sighting is sound, these instruments deliver accurate, repeatable results.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming any thermocouple equals “best” for high temperature. At very high temperatures and in radiant environments, non-contact methods often yield better accuracy and sensor life.

Final Answer:
radiation pyrometer