arranged to receive the syrup. Vacuum pans similar in construction to a 

 single cell of the evaporator, with dome-like tops and conical bottoms, with 

 heating surface arranged as a calandria, with top and bottom tube sheets 

 connected by copper tubes or with a series of copper heating coils, are used for 

 boiling syrups to a crystal. Leading from the top of the pan is a large vapor 

 pipe connected with a condenser. On the conical bottom is a large valve which 

 may be opened when the boiling is finished and the massecuite, or mixture 

 of crystals and molasses, is dropped into a receiving tank. 



The general principle involved in the boiling of sugar is the 

 Crystal- f 



lization separation or crystallization of the sucrose contained in a solution 



from the impurities, and this is accomplished by evaporation. 

 A portion of syrup is drawn into the vacuum pan as a charge, steam is turned 

 into the heating calandria and boiling begins. After the sugar is once formed 

 into fine crystals, these crystals attract the sucrose in the solution and continue 

 to grow in size rather than form additional crystals. By properly timed 

 admission of fresh concentrated juice, the crystals are provided with additional 

 sucrose, and thus the building up continues until the crystal has reached the 

 size desired by the sugar boiler. The crystal is pure sugar. The impurities 

 remain in the mother liquor and are carried off as molasses. It is not possible 

 to boil all of the syrup and molasses down to a crystal and at the same time 

 separate the pure sucrose from the impurities; therefore, enough moisture 

 must be left in the massecuite to permit separation of the crystals in the 

 drying process. 



The Drying of the Sugar Crystals 



When the sugar boiler decides that the massecuite has been 

 Mixers boiled to a proper density the whole contents of the vacuum 



pan are dropped into a receiving tank called a mixer. This mixer 

 usually is held just beneath the crystallizer floor and is of V-shape. To the 

 bottom of this mixer are attached machines used for separating the crystals 

 from the molasses. The mixer is equipped with paddles which are revolved so 

 as to keep the massecuite warm and prevent it from hardening before it 

 has been dried in the centrifugals. 



From the mixer the massecuite runs through gates into 



Machines centrifugal machines for the purpose of drying. The centrifugal 



basket is of tub shape suspended in the center by a spindle which 



is held at the top in a bearing attached to the bottom of the mixing tank 



44 



