Rotary kiln clinkering temperature: to obtain cement clinker from limestone and shale (or their slurry), the burning zone of a rotary kiln typically operates within which temperature range?

Introduction / Context:
In cement manufacturing, the raw meal must be transformed into clinker by solid-state reactions and partial melting. Knowing the appropriate burning zone temperature informs kiln operation, fuel selection, refractory choice, and quality control of clinker phases (alite, belite, aluminate, ferrite).

Given Data / Assumptions:

• Ordinary Portland cement process in a rotary kiln.
• Standard raw mix with limestone providing CaCO3 and clays providing SiO2/Al2O3/Fe2O3.
• We focus on the bed/clinker temperature rather than flame temperature.

Concept / Approach:
Calcination of CaCO3 begins around 850–900°C; belite forms around 1200–1300°C; alite formation and liquid phase development peak in the 1400–1450°C range. Therefore, the burning zone where clinkering is completed lies approximately between 1400° and 1500°C.

Step-by-Step Solution:
Associate key phase formation with temperature ranges.Identify the range that ensures adequate liquid phase and alite formation.Select 1400° to 1500°C as the correct operating window.

Verification / Alternative check:
Industry practice and kiln control charts target ~1400–1450°C clinker bed temperature for stable alite content and nodulization.

Why Other Options Are Wrong:

• 1100–1300°C: insufficient for alite; mainly calcination and early silicate formation.
• 1500–1600°C: excessive; risks refractory damage and is not operationally necessary.

Common Pitfalls:
Confusing flame temperature (higher) with clinker bed temperature; believing higher temperature always equals better clinker.

Final Answer:
1400° to 1500°C