Lining choice for bauxite calcination: rotary kilns used to calcine bauxite are commonly lined with which class of bricks to withstand temperature and chemical conditions?

Introduction / Context:
Bauxite calcination requires sustained high temperatures and exposure to alumina-rich dusts and vapors. Lining materials must offer adequate refractoriness, hot strength, and corrosion resistance without excessive cost or thermal mismatch. The question asks which brick class is typically selected for such rotary kilns.

Given Data / Assumptions:

• Bauxite calcination temperatures are high enough to stress ordinary fireclay bricks.
• Excessive cost or thermal expansion mismatch may disfavor ultra-pure corundum bricks except in special zones.
• Compatibility with alumina-rich environment is advantageous.

Concept / Approach:
High-alumina bricks in the ~80–90% Al2O3 range balance performance and cost for bauxite service. They exhibit higher refractoriness under load, better abrasion resistance, and improved corrosion resistance compared with fireclay. Carbon or silica bricks would be chemically or thermally unsuitable. While near-99% alumina bricks offer excellent properties, they are often reserved for hot spots due to cost; 85% alumina bricks are a widely adopted, robust choice for general lining in bauxite kilns.

Step-by-Step Solution:
Eliminate low-grade brick (fireclay) → insufficient at top temperatures.Eliminate silica and carbon → poor compatibility/oxidation risks.Choose 85% alumina → strong balance of hot properties and economy.

Verification / Alternative check:
Vendor recommendations and kiln case studies frequently specify 80–90% alumina linings for bauxite calcination, confirming the suitability of 85% alumina bricks.

Why Other Options Are Wrong:
Fireclay: inadequate RUL and abrasion resistance.Carbon: oxidation and contamination concerns.Corundum: excellent but often cost-prohibitive for full linings.Silica: thermal shock and chemical compatibility concerns.

Common Pitfalls:
Specifying ultra-high-alumina everywhere without economic justification.Underestimating abrasion from rotating bed and dust-laden gases.

Final Answer:
85% alumina bricks