Before enter the mills, cane is defibrated with knifes in a rotating shaft at a high speed. The product of this operation is squeezed in rollers mills, in a serial of four or five mills. In each mill there is, normally, three rollers, one in the top and two in the bottom. More modern mills use six rollers (Murry, 1998).
Sugar cane mills (six rollers)
In the first mill, cane is squeezed between the top roller and the bottom rollers. A juice is extracted, the first extraction juice. The resulting solids, the bagasse, are then squeezed in the following mills. Before the last mill (ex. fifth mill), water, the imbibition water, is added to the bagasse, in order to extract the maximum of sucrose. Juice from last mill is added to the bagasse entering the fourth mill. Juice from fourth mill will be mixed to bagasse entering third mill. The same happens with the juice of third mill, and bagasse entering the second one. Juice from second mill is mixed with juice of first extraction, forming the mixed juice. Bagasse from last mill is used as fuel for steam and power generation. This fact turns sugar mills, free energy consumption unities, which is a great advantage in comparison with beet sugar factories.
Murry C.R., 1998, Cane Mills, Section 6.3.3. of Sugar Technology, Ed. Poel P.W., Scieweck H., Schwartz T., Pub. Verlag dr.Albert Bartens, Berlin,360-374