Innovative Process for Boehmite Precipitation in Bayer Circuit

JNARDDC is intensely working toward the development of boehmite product hydrate as an intermediate product to reduce energy consumption in the calcination step. The innovative process of modifying the gibbsite seed property to boehmite and using it in precipitation has been thoroughly explored in the study. The investigations have shown that it can be produced in the precipitation circuit using boehmite seed hydrate under conditions different than that of gibbsite precipitation. Statistical design of experiments was applied, and liquor productivity achieved was 45–55 g/L at optimal parameters. Temperature and seed ratio are the most important facilitating factors for boehmite precipitation. Experimental results have confirmed that boehmite can be precipitated at 90–110 °C and with a caustic solution having a concentration of pregnant liquor of 145 g/L. Upon calcination at 600–700 °C, boehmite product hydrate generates alumina having properties very close to smelter-grade alumina. Characteristics of boehmite seed and product hydrate and alumina obtained by calcination of boehmite product hydrate have been explained in detail as well.