CHAPTER XX 

 THE SEPARATION OF THE CRYSTALS 



THE concentrated syrup discharged from the pan consists of a magma of 

 crystals and molasses. The molasses are separated from the crystals by 

 causing the magma to be rotated at a great velocity in perforated baskets. 

 In this way the whole mass is forced against the perforated wall, the molasses 

 passing through the wall of crystals and the perforations in the basket. 

 The machines employed are known as centrifugals or hydro-extractors. 

 From one point of view this process may be regarded as one of filtration 

 under great pressure. 



Receptacles for and Transport of Massecuite. In modern factories the 

 high-grade massecuites, which are dried without preliminary cooling, are 

 discharged into large receptacles capable of holding a full strike of the pan. 

 These tanks, which are usually cylindrical or U-shaped, and provided with 

 stirring gear, may be placed directly over the battery of centrifugals or 

 underneath the pans. In this case the centrifugals are provided with a smaller 

 receiver, into which the massecuite is fed. This smaller receiver also con- 

 tains a stirring gear usually operated by a sun and planet motion. From this 

 tank individual charging spouts lead to each machine. 



The most convenient system of handling is one operated by gravity. 

 In districts, however, where cyclones or earthquakes occur a tall building 

 is dangerous ; in this case it is usual to place the receptacles on the ground 

 floor and to elevate the massecuite to the centrifugal supply tank by means 

 of magma pumps, chain pumps, or preferably by compressed air. 



An earlier system included the use of tanks running on tramways, from 

 which the massecuite was shovelled to the centrifugal supply tank. In a 

 second scheme once widely used the massecuite was discharged into cans 

 holding about 500 Ibs., which were transported on trucks to a hydraulic 

 elevator, their contents being dumped into the centrifugal supply tank. 



Early Methods of Separation. The original method of separating the 

 crystals from the molasses was drainage, and to this day this method is still 

 used in a few districts, the massecuite being packed into hogsheads with 

 perforated bottoms. 



Pressure on the massecuite in cloth bags was patented by Wakefield 

 (2506, 1801), and drainag;e into a vacuum by Vaughan (3261, 1809). Hague 

 (4048, 1816 ; 5725, 1828) also patented vacuum drainage, adding thereto 

 the use of compressed air on the surface of the massecuite ; this process was 

 extensively used in London refineries, and also in the raw sugar industry. 



The removal of the adhering molasses, and its substitution by a clairce 

 of high-grade syrup, is seen in Constant's patent (3541, 1812), and is also 



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