GB763291A - Process and apparatus for the separation of insoluble protein from a starch suspension - Google Patents

Abstract

763,291. Centrifugal separators. STAMICARBON, N. V: July 15, 1954 [July 17, 1953], No. 20709/54. Class 23 [Also in Group V] In separating insoluble proteins from a liquid suspension of starch, e.g. a suspension obtained in a maize starch mill, the suspension and a gas, e.g. air, are fed continuously into a hydrocyclone or multihydrocyclone 18, Fig. 1, to form a froth to which the proteins adhere. The issuing apex fraction 23 is rich in starch and poor in froth. The overflow fraction 22, which is rich in froth and poor in starch, is passed to a froth separator 2 from which froth and protein particles are discharged at g. Defrothed liquid 30 containing starch particles may be returned to the hydrocyclone. The gas b may be drawn into the suction pipe 19 of a pump 17 feeding the hydrocyclone. In the lay-out according to Fig. 2, the apex fraction 23 passes into a froth separator 26 from which froth 24 is taken to a reservoir 16 supplying the pump 17. Defrothed liquid 28 rich in starch is pumped into the tank 35 of purifying apparatus comprising further tanks 41, 47, 53, 59, 65, multi-hydrocyclones 38, 44, 50, 56, 62, 68, and pumps 37, 43, 49, 55, 61, 67. Concentrated starch fractions are discharged from the apex apertures of the multi-hydrocyclones; solid and dissolved impurities from their overflow apertures. Each multi-hydrocyclone is fed with the apex fraction of the preceding and the overflow fraction of the following multi-hydrocyclone. Wash water w is supplied to the last tank 65. The froth separator 26 may be omitted. Impurities 39 leaving the apparatus are returned to the tank 16. Purified starch suspension 70 flows into a tank 71 and then into a centrifuge 73 from which dewatered starch s is discharged and subsequently dried. Liquid passes from the centrifuge into a tank 76 from which it is pumped to hydrocyclones or multihydrocyclones 80, 82, 84. The overflow k from hydrocyclone 84 may be used as wash water. The apex fractions 87 and 88 from hydrocyclones 82 and 84 are returned to the tank 76. The apex fraction 86 from hydrocyclone 80 is returned to the centrifuge. In the modified layout according to Fig. 4, the starch suspension is pumped from the reservoir 16 into a multi-hydrocyclone 18<SP>1</SP> whose apex fraction passes into a multi-hydrocyclone 18<SP>11</SP>, whose apex fraction 23 is pumped to the tank 35. The overflow from multihydrocyclone 18<SP>1</SP> passes into multi-hydrocyclone 18<SP>111</SP>, whose overflow passes into multi-hydrocyclone 18<SP>1111</SP>, whose overflow 22 passes through a froth separator 27 into a settling tank 109. The apex fractions from multi-hydrocyclone 18<SP>111</SP> and 18<SP>1111</SP> are returned to the reservoir 16. The overflow 39 from the multi-hydrocyclone 38 is fed into a multi-hydrocyclone 100 whose overflow passes through a froth separator 103 into a settling tank 106. The multi-hydrocyclones comprise from 90 to 800 individual hydrocyclones each comprising a short cylindrical part 90 closed by a cover 94 provided with a vortex-finder 95 and an overflow aperture 96, a feed pipe 92 entering the cylindrical part tangentially through an aperture 93 and a conical part 91 having an apex discharge aperture 97. The apex angle may be 6 degrees or 8 degrees. The height of the part 90 may be 4.5 mm. and its diameter may be 10 mm. The diameter of the apertures 93, 96, and 97 may be 2.5 mm. The vortex finder may intrude 4.5 mm. into the cylindrical part.