Patent GB-811686-A (GB)
Title: A wet starch manufacturing process
IPC: C08B30/04
Filed: 1957-03-14
Abstract: <PICT:0811686/IV (a)/1> Starch-bearing grain is subjected to steeping, cracking and germ removal operations to provide a wet degerminated material containing the hull and unmilled endosperm which is fed into a high speed rotating rotor disc which imparts its velocity to the material and impinges it upon a surface, the impact of which is substantially normal to the direction of the material whereby starch and gluten are separated from the fibre without shredding it; the peripheral speed of said rotating disc being at least 21,000 feet per minute.  The apparatus used is an impact mill (Fig. 1) consisting of a rotating element 3 equipped with equally spaced impactor pins 4 encased in a housing 10 and rotated by a shaft 1 and pulley 2.  The housing is equipped with equally spaced stationary pins 5 and the bottom of the housing is cone shaped to collect and discharge the treated material.  For best results the rotor pins should be 3/4 inch in diameter and for the 27-inch rotor there should be 72 pins spaced at about 1 8/1 inches apart.  The spacing between the rotor pins should be not less than 1/2 inch and not more than 1 1/2 inches.  For the 27-inch rotor there should be 84 stator pins in the housing 3/4 inch in diameter and spaced 1 1/16 inches apart. The clearance between the rotor and stator pins should be from 1/2 to 2 inches.  In operation, the wet degerminated material to be processed 7, having a moisture content between 65 and 90 per cent, is fed into rotor 3 at or near the centre and passed outwardly to the rotor pins 4 where it is accelerated in the direction of rotation and then discharged to the stator pins 5.  The treated material is then discharged through outlet 6, and is then subjected to screening and washing operations in conventional manner with bolting cloth.  The mill starch stream separated from the fibre is separated into starch and gluten in customary manner, e.g. by centrifuges.  In the overall process (Fig. 2, not shown), the corn is subjected to the action of warm sulphur dioxide solution in a steep tank, and then roughly milled (e.g. in an attrition mill) for germ removal and passed to a separator in which the ground grain and germ fraction are separated.  Fibre and starch slurry from the separator are passed over a dewatering screen and the fibre is remilled on an attrition mill.  The filtrate from the screen is re-introduced before the ground slurry enters a second separator.  The fibre and starch slurry from this separator pass over a double-deck shaker to the impact mill and the fibre in the mill discharge is separated from the starch slurry on a screen.  The filtrates from this screen and the double-deck shaker are combined to produce mill starch which is separated into a starch underflow stream and a gluten overflow stream in conventional manner, e.g. by centrifuges.  The process waters from the gluten overflow are returned to the steeping process and the process waters from the starch underflow are re-used in the process at a stage later than the process waters from the gluten overflow. Fresh water is introduced to wash the starch and the countercurrent system is used.  The fibre may be washed and treated in a second impact mill, again washed, dewatered and dried.ALSO:<PICT:0811686/IV (b)/1> Starch - bearing grain is subjected to steeping, cracking and germ removal operations to provide a wet degerminated material containing the hull and unmilled endosperm which is fed into a high speed rotating rotor disc which imparts its velocity to the material and impinges it upon a surface, the impact of which is substantially normal to the direction of the material whereby starch and gluten are separated from the fibre without shredding it; the peripheral speed of said rotating disc being at least 21,000 feet per minute.  The apparatus used is an impact mill (Fig. 1) consisting of a rotating element 3 equipped with equally-spaced impactor pins 4 encased in a housing 10 and rotated by a shaft 1 and pulley 2.  The housing is equipped with equally spaced stationary pins 5 and the bottom of the housing is cone-shaped to collect and discharge the treated material. For best results the rotor pins should be 3/4 inch in diameter and for the 27 inch rotor there should be 72 pins spaced at about 1 1/8 inches apart.  The spacing between the rotor pins should be not less than 1/2 inch and not more than 1 1/2 inches.  For the 27-inch rotor there should be 84 stator pins in the housing 3/4 inch in diameter and spaced 1 1/16 inches apart.  The clearance between the rotor and stator pins should be from 1/2 to 2 inches.  In operation, the wet degerminated material to be processed 7, having a moisture content between 65 and 90 per cent,  is fed into rotor 3 at or near the centre and passed outwardly to the rotor pins 4 where it is accelerated in the direction of rotation and then discharged to the stator pins 5.  The treated material is then discharged through outlet 6, and is then subjected to screening and washing operations in conventional manner with bolting cloth.  The mill starch stream separated from the fibre is separated into starch and gluten in customary manner, e.g. by centrifuges.  In the overall process (Fig. 2, not shown), the corn is subjected to the action of warm sulphur dioxide solution in a steep tank, and then roughly milled (e.g. in an attrition mill) for germ removal and passed to a separator in which the ground grain and germ fraction are separated.  Fibre and starch slurry from the separator are passed over a dewatering screen and the fibre is remilled on an attrition mill.  The filtrate from the screen is reintroduced before the ground slurry enters a second separator. The fibre and starch slurry from this separator pass over a double-deck shaker to the impact mill and the fibre in the mill discharge is separated from the starch slurry on a screen.  The filtrates from this screen and the double-deck shaker are combined to produce mill starch which is separated into a starch underflow stream and a gluten overflow stream in conventional manner, e.g. by centrifuges.  The process waters from the gluten overflow are returned to the steeping process and the process waters from the starch underflow are re-used in the process at a stage later than the process waters from the gluten overflow.  Fresh water is introduced to wash the starch and the countercurrent system is used.  The fibre may be washed and treated in a second impact mill, again washed, dewatered and dried.