1912.] 



The Production of Beet Sugar. 



1009 



The vapour from the fourth vessel now passes, as a rule> 

 through juice heaters where as much as possible of its remain- 

 ing heat is utilised. It then passes on to the condenser. This 

 vapour is at a very low tension. In order to maintain a 

 vacuum in the condenser, it has to be provided with an air- 

 pump to draw off all incondensible gases, which are always 

 more or less mixed with the vapour, and which would other- 

 wise accumulate in the condenser. It will be seen that 1 lb. 

 weight of steam (as measured in a closed vessel) evaporates 

 nearly its own weight in each of these vessels, i.e., it has 

 almost a fourfold economy. 



The thick juice from the evaporators is pumped to 

 another carbonatation or sulphitating installation and 

 after treatment is again filtered and passed on to the 

 vacuum-pan supply tank and thence to the vacuum pans 

 (see Fig. 3). 



This final evaporation of the concentrated juice in the 

 vacuum pans is also performed in a comparatively high 

 vacuum, in order that the sugar may boil at a very low 

 temperature, and thus not subject the crystals to carameU 

 isation or "burning." The vapour issuing from the vacuum 

 pans is also condensed in a condenser provided with an air- 

 pump. 



In most modern factories there is only one condenser in the 

 whole factory, which serves for both the evaporators and 

 vacuum pans. This thick juice in the vacuum pans is boiled 

 until it reaches a condition known as " massecuite," i.e., a 

 mixture of well defined crystals and concentrated syrup. This, 

 "massecuite" is now discharged into crystallisers where it 

 is cooled down by stirring, thus allowing the "grain" to 

 grow, and it is afterwards passed to the centrifugals, which 

 by the rapid revolving action separate the crystals from the 

 adhering syrup, the latter passing through the finely perforated 

 periphery, leaving the crystals of sugar adhering to the sides, 

 of the centrifugal basket. 



This first sugar has a polarisation of about 96 per cent, to 

 97 per cent. The syrup is again treated by boiling, etc., as 

 before, and after passing through a second lot of centrifugals 

 yields a sugar having a polarisation of about 90 per cent. The 



