THE EXTRACTION OF JUICE BY MILLS. 



of the emergent juice and fibre, is7rx60x30x^ cubic inches. For 

 lack of a better term this volume will be referred to in the sections immediately 

 following as the escribed volume. 



In the megass mills it is customary to set the top and back rollers 

 practically metal to metal, and hence to allow the megass to pass, the rollers 

 must become separated by a certain distance, which can be obtained by the 

 calculation given below. 



Let there be a mill of dimensions 60 in. X 30 in. running at the rate of 

 two revolutions per minute; let 25 tons of cane carrying 12 per cent, of fibre 

 be crushed per hour; let the megass as it leaves the mill contain 45 per cent. 

 of fibre and 55 per cent, of juice; let the density of the juice be 1*07 and of 

 the fibre be 1-35. Then in one hour there pass 3 tons of fibre and 3'66 tons 

 of juice. The volume of the fibre passing per hour is 



3 X 2240 

 62-25 x 1*35 = ^ 9 ' 96 c * ft- an( ^ ^ at ^ *ke J u * ce * s 



- 123-19 c. ft.; and together 203-15 c. ft. 



To allow this quantity to pass, the escribed volume must not be less; 

 the crushing surface per revolution is ~TTT sq. ft. = 39-28 sq. ft. ; 



so that at a speed of two revolutions per minute the minimum opening 



20S* 1 5 

 between the rollers is 39.28 x 120 ~ ' 43 ft> = ** in ' 



If the rollers ran at 2'5 revolutions per minute, the minimum opening 

 works out at ff in., so that with high speeds a smaller opening is necessary. 



In actual practice the megass and top rollers are set metal to metal, and 

 not to such relatively large distances as the above calculation implies; the 

 volume necessary for the megass to pass is made up of the spaces formed by 

 the grooving of the rollers, by roughness in their surface, and also by actual 

 distortion and forcing apart of the rollers. 



In the above conception it is necessary to distinguish between the actual 

 and the apparent volume of the megass ; the latter is the space occupied by 

 the megass and includes the intercellular and interstitial spaces, and depends 

 upon the structure and packing of the fibre ; the former is the least volume 

 into which the megass could be packed on the supposition that the space 

 is filled wholly with megass. 



Capacity of Mills. It is easy to see that, provided all other con- 

 ditions remain constant, the capacity of a mill is fixed by the escribed 

 volume, and hence if two mills of different size be run at the same peripheral 

 speed, that the capacity is fixed by the crushing surface. There are, however, 

 many factors that do not remain constant, and which can be varied at will, so 

 that so simple a relation does not hold. As a matter of empirical observation 



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