TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The impact milling is carried out on wet corn to preserve the largest possible average particle size of the milled fractions, with separation of the bran by friction. The germ is subsequently crushed to facilitate its size separation. The impact milling is carried out using an impactor. The impactor has moving blades with with impact surface relatively large with respect to the other dimensions of the blades. The impact surface moves substantially perpendicular to a moving direction of the blades. The blades move at less than 70 (35) m/s. The blades are mounted on a rotor and extend at least 30 (60) mm from the rotor. The throughs (6) in output from the mill (5) are sent to a first rotary separator (8), which separates the grits from the throughs and a corresponding reject (10). The reject (7) that arrives from the mill (5) is sent to a first separator (11) from which a stream (12) of light fractions and a stream (13) of grits, germ and residual bran exit. The latter stream is subsequently sent to a second station (14) for wetting with water and to a first roller mill (15), in which the germ is crushed to facilitate subsequent size separation of germ and grits in a first sieve (16). The stream of intermediate product (19) in output from the sieve (16) is added to the reject (10) that arrives from the rotary separator (8) and is passed through a second separator (20) from which a stream (21) of light fractions and a stream (22) of grits, germ and minor amount of residual bran exits. The stream of grits (22) is sent to a second roller mill (23), in which additional crushing of the germ is performed to facilitate its subsequent size separation in a second sieve (24). The light fractions from different separators are conveyed to a pneumatic settling unit (31), from which an output (32) for bran and any fine grits fractions and an output (33) of dusty air lead out (where the air is conveyed in turn into a manifold to be sent to the bag filter). The output is sent to a second rotary separator (35), which divides the stream into a grits output and a corresponding waste formed by bran (where the output of grits that arrives from the air stream is further separated in the filter). EXAMPLE - Corn was treated with water (40 l/h) for 55 minutes. The extracted product was feed in to the mill. The rejects and the throughs of the mill were 2936 kg/h as the coarse fraction part and 1014 kg/h as a fine fraction, respectively. The troughs were graded in the first rotary separator, from which products (64 kg/h) were separated, while the remaining reject (948 kg/h), was conveyed to the second pneumatic separator. The reject (2936 kg/h) from the mill was passed through a pneumatic separator, which separates light product (137 kg/hour) by an air stream. The remaining product (2799 kg/hour) was treated by adding water in a second wetting station (12 l/h) without resting and then milled through the first roller mill pass. The reaction mixture was worked up to give ethanol.