Opportunities for Using Bauxite Residue in Portland Cement Clinker Production 2020

The prospects for using bauxite residue in Portland cement has been explored for over 80 years with many promising technical studies and several successful large-scale commercial initiatives. The iron and aluminium compounds contained in the bauxite residue provide valuable additions in the production of Portland cement at a low cost.

The best estimates are that over 1,500,000 tonnes of bauxite residue are currently used annually in the production of Portland Cement clinker. The cement plants currently utilising the bauxite residue in clinker production are based in China, Ukraine, India, Russia, Georgia, Moldova, Cyprus and Greece.

From the evidence from the cement plants that are already using bauxite residue on an industrial scale, it is clear that bauxite residue can satisfactorily be used in cement clinker manufacture with only slight changes to their operating process. With the appropriate bauxite residue, typically a usage rate of 3 to 5 % can be accommodated. From the industrial experience to date, key aspects seem to be:

• a relatively low moisture content – approximately 30 % moisture has been used in several plants and this can readily be achieved by bauxite residue producers, some alumina refineries have used a plate and frame filter press to produce a satisfactory product whilst others have reached a satisfactory level by air drying the bauxite residue
• a moderately low sodium content, a value of <2.5 % Na2O has been indicated as satisfactory but it will depend on the composition of the other raw materials
• the appropriate aluminium oxide to iron oxide ratio (an iron oxide to alumina ratio of 0.8:1.2 in the raw mix was found to give the best results in one study although some plants will use the bauxite residue to supplement the iron level whilst others use it for the alumina content)
• the reasonable proximity of a cement plant (up to 1200 km has been found to be acceptable in one case).