Alumina Production Carbonation Mother Liquor Causticizing Process Study

An improved process for the causticization of mother liquors in Sintered alumina refinery has been studied. The technology includes that the green liquors is precipitated by introducing carbon dioxide to produce the alumina trihydrate, then part of the mother liquors is causticized with lime, and then is returned to desiliconizing system of the raw liquors to increase the liquor's α_k.In the Shandong Aluminum Corporation, the green precipitating system includes two side-streams, one is for the carbonation, and another is for seeding precipitation. As is well known, there are some disadvantages in seeding precipitation process such as long the residence time for suitable alumina trihydrate output, the fine grain of alumina trihydrate product with fluctuating granularity, ineffectual cycle of a certain quantity of alumina in the process, etc. However, there exist some advantages in the carbonation process such as the shorter residence time than that in the seeding process for suitable alumina trihydrate output, the coarse grain of alumina trihydrate product, and the high alumina output.It is shown that the present improved process can overcome the disadvantages occurring in the seeding precipitating process. It indicates that the lime efficiency and causticizing efficiency can be up to 90% and over 80% respectively in the new process, which is feasible in technology, and rational in economy.