THE FILTRATION OF THE JUICE. 



Mechanical Filtration. Filtration of the juice after separation 

 from the scurns is practically universal in beet sugar factories and should 

 always be made in cane sugar factories where high-class sugars are 

 being made ; the nitration is made in what are termed mechanical filters, 

 a large number of different designs, differing only in detail, being in 

 existence. 



In Fig. 155 are shown sections at right angles to each other of a common 

 type. The filter consists of an iron box provided with a false lid in which 

 are k fixed frames a. These frames consist of a lattice work skeleton over 

 which is stretched a woven fabric, each frame is complete in itself and is 

 called an element. A separate outlet is provided for each element so that any 

 faulty ^one can be shut off. All the elements discharge into one common 

 gutter. The juice enters the box at d, fills the box below the level of the 



FIG. 155. 



false lid and passing from the outside to the inside of the elements discharges 

 at b. In the form shown the elements are rectangular, while in some other 

 designs they consist of cylinders, but the principle is the same in all. These 

 filters are generally made with elements of one square metre filtering area, 

 counting, of course, both sides, and in a chamber there will usually be about 

 twenty to thirty elements. The filters will pass on an average 10 gallons 

 of juice per square foot per hour, but as much time is lost in changing cloths, 

 they should not be calculated to pass more than seven gallons per foot per 

 hour. They are also sometimes used to filter syrup on its way to the pans 

 from the triple. When used for this purpose, their capacity is only one-third 

 or one-fourth of what it is for juice. They are usually worked under a head 

 of 6 or 7 ft. 



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