| 摘要 |
The precipitate formed during clarification of sugar solutions by means of lime and carbon dioxide (sediment from carbonation) is separated into different fractions by elutriation, and water is removed by filtration or centrifugal action from a middle fraction to yield a purified calcium carbonate. Dry, moist or suspended sediment from carbonation may be bleached, if necessary, before, simultaneously with, or after elutriation, with reducing- or preferably oxidizing-bleaching agents such as chlorine or chloride of lime; if desired the bleached product may be coloured by conventional means. The sediment from carbonation can be fired to remove the organic substances prior to elutriation, below the dissociation temperature of CaCO3. In the example, sediment from carbonation was separated by elutriation into 14 fractions, of which fractions 2 and 3 were suitable for the production of pure calcium carbonate and fractions 3-5 were suitable for the production of chalk-like substances, the organic substances serving as binders for this purpose (fraction 1 being the heaviest). |
