Process Analysis Of The Bayer Process For The Preparation Of Sodium Metaaluminate

Sodium metaaluminate Bayer method uses bauxite as raw material, and requires its alumina content to be 40% to 70%, silicon dioxide to be 4% to 20%, and iron oxide to be 1% to 20%. The mass ratio to silicon oxide is greater than 8. The bauxite is pulverized and ball milled to make the particle size reach 85% and pass through 220 mesh, then mixed with lye and wet-milled for high-pressure dissolution, heated at 150°C for 2 to 3 hours, and the alumina in the bauxite is transferred in the form of sodium aluminate solution, while impurities such as silicon oxide, iron oxide, and calcium oxide become red mud and precipitate. In order to make the sodium aluminate solution easy to separate from the red mud and strengthen the desiliconization, the eluate can be diluted until the alumina content is reduced from 250-300g/L to 100-120g/L. The sodium aluminate solution and red mud are separated in the multi-layer settling tank, and then the sodium aluminate solution is evaporated to dryness to obtain the finished product.
The Bayer method is suitable for bauxite with low silicon content. The process is simpler than the sintering method, with less investment, lower cost and high product quality. However, when the grade of bauxite being processed is low, its economic advantages are also Then lower.