The production process of alumina for polishing

There are various methods of extracting alumina from ore: Bayer, soda-lime sintering, combined Bayer-sintering, etc. The Bayer method has always been the main method for producing alumina, and its production accounts for about 95% of the total alumina production in the world.

Bayer method:

The principle is to use caustic soda (NaOH) solution to dissolve the alumina in the bauxite ore by heating to obtain sodium aluminate solution, after the solution is separated from the residue (red mud), the temperature is lowered and aluminium hydroxide is added as crystal seed, after a long time of stirring, the sodium aluminate decomposes and precipitates aluminium hydroxide, which is washed and calcined at a temperature of 950 to 1200℃, and then the finished alumina is obtained. The solution after the precipitation of aluminium hydroxide is called the mother liquor, which can be recycled after evaporation and concentration.

The advances of the modern Bayer method:

1) The enlargement of equipment and continuous operation.

2) The automation of the production process.

3) Energy savings, such as high-pressure intensive dissolution and fluidised roasting.

4) The production of sand alumina to meet the needs of aluminium electrolysis and dry flue gas purification.