Preferred Classification Equipment for Ground Bauxite Slurry

Hi Friends,

In earlier posts, we have discussed about various techniques for grinding of bauxite. The basic objective of grinding of bauxite is to increase the surface area of material substantially so as to improve its reactivity with caustic soda to a desired level during digestion process. As such wet grinding of bauxite has  been found to be energy efficient and environment friendly as well. Ball mill or Rod mill or SAG or combination of any two is generally used in Alumina refineries for the purpose. The particle size of ground bauxite is decided based on the laboratory test work ranging from 149 microns to 1000 microns, however, minus 10 mesh size (100%) has been found to be optimum size in most of the operative Alumina refineries in the World.

In present post, we will discuss the preferred equipment for classification of bauxite slurry in Alumina refinery. Though, open circuit wet grinding may require less capital investment as well as lower energy consumption but it is difficult to ensure desired product fineness. Thus, to ensure the consistency in desired product fineness, closed circuit grinding is adopted in most of the Alumina refineries. For bauxite slurry classification, any one of the following type of equipment are installed in Alumina refineries-

• DSM Screens, 
• Banana Screens,
• Hydro-cyclones.

With regard to capital investment for installation, all three types of slurry classification systems are comparable. But observing the availability for continuous operation, hydro-cyclones are always rated at number one position. The reason being it does not require any descaling and thus downtime is minimal where as periodic descaling of DSM as well Banana screens are mandatory for removal of accumulated scales to ensure desired classification efficiency. Hence considering the availability, reliability and process efficiency, hydro-cyclone is always the preferred classification for Bauxite grinding circuit.

I personally like trouble-free operation of hydro-cyclones over others and love to operate it efficiently. This is purely my personal experience. In case, you differ to my views, please come forward in freely exchanging your own operating experience. We will welcome your views.

regards.

Rajendra Kunwar
www.ceti.co.in