THE EVAPORATION OF THE JUICE TO SYRUP. 



Apparatus for multiple evaporation may be divided into three classes: 



1 . Vertical submerged tube apparatus, often referred to as the * standard* 

 type. 



2. Horizontal submerged tube apparatus, conforming to the original 

 Rillieux and including the Welner-JelineJc apparatus. 



3. Film evaporators, including the Lillie, Yaryan, and Kestner 

 patents. 



Vertical Submerged Tube Evaporator.- In Fig. 158 is 

 shown a section of one vessel of a vertical tube apparatus. At a are the tubes 

 outside which circulates the heating steam, the juice being contained within 

 the tubes and above and below the tube plates ; at b is an opening in the 

 centre of the tube plate forming a large central circulating tube ; at c is the 

 juice intake pipe dipping down to near the bottom of the vessel ; at d is a pipe 

 through which is drawn off the condensed water ; at e is a pipe through which 

 the incondensible gases are drawn off. 



The Calandria or tubular cluster consists 

 of two tube plates into which are expanded 

 the tubes ; the tube plates are usually fixed 

 to the wall of the containing vessel, but in 

 some designs the calandria has its own side 

 walls, an annular space being then formed 

 between the interior of the vessel and the 

 exterior of the calandria. The large 

 central tube is for the purpose of providing 

 a circulation, and is very generally found; 

 in other designs the circulating tube is not 

 placed centrally, but at the side. The 

 tubes are usually made of brass, but 

 copper is sometimes used, and in some 

 German designs the tubes are made of 

 mild steel. The diameter of the tubes 

 is generally about two inches ; in earlier 

 plants the length of the tubes reached up 

 FIG. 159. ag much as s j x f ee or more> tut now 



four feet is a usual length ; it will be shown later that a great length of 

 rtube may be detrimental to the efficiency. 



The distribution of the heating steam has a great effect on the efficiency ; 

 ; if the steam enter at one place only, that part of the heating surface remote 

 from the steam entry tends to become inefficient, and there is also a tendency 

 for incondensible gases to bank up. In the design shown the heating steam 

 ^passes into a belt surrounding the calandria ; in other designs the steam or 



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