254 



CHAPTER XII 



battery, of which four cells are effective, one, /, being filled, and one, e, 

 being ready to be emptied. The cell i has been filled with fresh chips. By 

 means of compressed air, water that has been admitted to cell e is forced 

 out of that cell, and is transferred to cell 4 and an equal quantity of water 

 or rather dilute juice in cell 4 passed on to cell 3, and so on. The material 

 in cell 2 passes on to cell i, which contains fresh cane chips which have not yet 

 come into contact with water or dilute juice. Water pressure from an 

 overhead tank is now applied 'to cell 4, and a similar forward movement 

 obtains, and in this case material is withdrawn from cell i ; the quantity 

 drawn being equal in volume to the water admitted to cell 4. Cell 4 is now 

 treated as cell e in the first operation, and in the meantime cell e has been 



filled with fresh cane, and the 

 above - described routine again 

 takes place. By following out 

 this process it is seen that when 

 there are n effective cells in opera- 

 tion, fresh cane comes into con- 

 tact with water or dilute juice 

 2n-i times before it is finally dis- 

 charged from the battery. 



For more detailed information 

 on the operation of diffusion 

 batteries, reference should be 

 made to any standard work on 

 beet sugar manufacture. 



Extraction in a Diffusion Bat- 

 tery. The general equation ob- 

 tained for compound maceration 

 in a milling plant gives also the 

 extraction in a diffusion battery, 

 that is to say, if there are n diffu- 

 sions in a round of the battery 

 where the extraction in each 

 operation is r, then the total ex- 

 traction is T 



r-(L-r) n 



FIG. 152 It is evident from this equa- 



tion that the extraction increases 



as both r and n increase. The value of r increases with the completeness of 

 the diffusion whereby a time factor is introduced, and also with the quantity 

 of material passed from cell to cell in each operation. At' the same time, 

 however, increasing the " draw " increases the dilution. At the time that 

 diffusion'plants were operated, the dilution was about 30 per cent., and the 

 extraction from 95 per cent, and upwards of the sugar in the cane. 



Mixed Extraction Processes. As early as 1850, experiments in the system- 

 atic lixiviation of bagasse were made in the French West Indies, and since 

 that time several schemes have been prominent, and, as long ago as 1883, 

 bagasse diffusion was successfully operated at Torre del Mar, in Spain. 2 

 The most recent attempts in this direction have been that of Kessler, U.K. 

 patent 15355 of 1902, who proposed a U-tube through which the bagasse was 



