Sugar refinement is the process by which raw sugar or beet sugar becomes white refined sugar. Sugar typically comes from one of two vegetable sources: sugar cane or sugar beet.
Cane sugar mills are responsible for the production of sugar that contains molasses—giving the sugar the characteristic brown color. White crystallized sugar is over 99 percent sucrose and is highly refined to remove residual beet flavors.
Many sugar mills operate during the time of harvest. In the case of sugar beet refineries, the time during and immediately following harvest is critical for beet processing and sugar production. For cane sugar refineries, they are either at full production during harvest season or they refine sugar steadily throughout the year. Raw sugar gets converted into white refined sugar in local refineries where it is sold to the local population or it is exported then refined later.
Sugar refineries are generally located where the consumption of sugar is greatest. North America, Europe and Japan represent the largest sugar consuming regions of the globe. Although in recent years the Middle East has increased its sugar refinery production and output, the largest producer of sugar in the world is in North America.
Raw sugar is generally stored in large warehouses where it is moved into the refinery via conveyor belts. Sugar beets are sliced, and sugar is extracted via a process of diffusion and presses, whereas raw sugar from cane is mixed with heavy syrup and centrifuged to extract the sugary crystals.
Clarification is achieved by mixing phosphoric acid and calcium hydroxide which form calcium phosphate. Once the sugar is reduced into a syrup form, calcium phosphate is added. Purification is achieved by the work of calcium phosphate particles that collect impurities and float to the top of a tank. After entrapping impurities they are easily removed via skimming or filtration. Carbon dioxide may also be used at this step. A similar outcome takes place where the filtered precipitate is calcium carbonate instead of calcium phosphate.
Evaporation reduces the volume of the syrup, causing it to be thicker and more saturated with sugar. Through a continuous process of boiling and drying in large vessels, the mass gradually changes from a liquid to a solid. After washing and further refinement, white crystal sugar eventually is produced.