THE SEPARATION OF THE CRYSTALS. 



Sugar Driers* Sugar driers are used to dry white plantation refined 

 sugars and also find a use in drying the rather low grade sugars resulting from 

 crystallization in motion schemes. A view of a form of drier is shown in 

 Fig. 216 ; it consists of an inclined cylinder a a which is caused to revolve 

 about a longitudinal axis, power being received from a belt at the pulleys 

 b ; inside the cylinder are a number of shelves which throw the sugar about 

 in passage ; the wet sugar enters through the shoot c and leaves at d ; hot 

 air heated by passing over the steam heated coils at e passes through the 

 cylinder and leaves at /under the influence of a fan. In the Hawaiian islands 

 the sugar occupies about five minutes in its passage through the apparatus 

 and reaches a temperature of about 180 F., the moisture falling from about 

 1'5 per cent, to about '5 per cent. 



Druelle Say Process. 4 However carefully the massecuite is 

 boiled, a certain amount of fine grain is formed which passes through the cen- 

 trifugal mesh ; this process aims at recovering this loss through the agency of 

 filtration ; the molasses containing the fine grain are passed through filter 

 presses of conventional design, the cake of fine grain which forms in the 

 presses being dissolved in the thin juice. 



Experimental Study of Centrifugals. The various questions 

 that arise with regard to the treatment of massecuite in the centrifugal have 

 been carefully studied by Geerligs 5 . He determined first from actual factory 

 experiments the yield in the same massecuite when boiled to different degrees 

 of concentration and found that although more sugar separates out in close 

 boiled than in more open boiled massecuite, the yield in crystals is not 

 augmented, as more water is required to remove the more viscid molasses ; on 

 the other hand, there is a limit to the amount of water which should be left ; 

 he found the best results were obtained when the true water content was 8 per 

 cent, to 9 per cent., corresponding to an apparent water content of 5 per cent, 

 to 7 per cent. 



He found too, that when impure massecuites were cured hot, direct from 

 the pan, practically the same amount of crystals was obtained as when 

 cured cold, but that with pure raassecuites considerably more crystals were 

 obtained when cured cold. This result is of course due to the sugar in the 

 impure massecuite, when cooling, separating as small grain ; in the pure 

 massecuite of less viscidity, to the sugar separating on grain already 

 present. 



As a general rule the amount of sugar present as crystals is very much 

 the same in all first massecuites of both high and low polarization, and it is 

 the form and shape of the crystals that control the yield in the centrifugal. 

 This point is of such interest that the following table due to Geerligs is 

 reproduced here, where it will be plainly seen on inspection that the purer 



385 



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