Patent ID: 7015167

Claim:
A high-alumina raw material, comprising in weight-percent, based on dry weight: Al 2 O 3 50–80% MgO 2–15% SiO 2 1–15% CaO 0.5–20% Fe 2 O 3 0.5–2% Na 2 O 0.5–2% Al (metallic) 0.1–2% AlN 0.1–1% K 2 0 0.1–1.5% F 0.1–2% Cl 0.1–0.8% other 5% components, not to exceed loss on ignition, not to exceed 15% and wherein the mineral form of Al 2 O 3 comprises, in weight-percent: aluminium hydroxide 20–60% corundum α-Al 2 O 3 10–40% spinel MgAl 2 O 4 5–40% wherein the aluminium hydroxide is present as aluminium mono-hydroxide Al 2 O 3 .H 2 O and aluminium tri-hydroxide Al 2 O 3 .3H 2 O with a weight ratio between Al 2 O 3 .H 2 O and Al 2 O 3 .3H 2 O exceeding 0.25.