THE EXTRACTION OF JUICE BY MILLS. 



Compound Saturation. The highest possible efficiency of the- 

 added water is obtained, when the diluted juice from a later mill is used as a 

 saturating agent on the megass coming from a previous one ; an algebraical 

 expression showing the effect of this procedure is not easy to obtain, and 

 when obtained is not elegant ; the effect of this way of working is best 

 shown by a worked out example : 



Let canes containing 12 per cent, of fibre be dry crushed to 45 per cent^ 

 of fibre in the first nine rollers of a twelve -roller mill ; let water 30 per cent, 

 on weight of cane be now added to the megass with complete admixture, and 

 let the saturated megass be crushed to 50 per cent, of fibre ; then applying 

 the equations established above, in the dry crushing an extraction of 85-8 per 

 cent, is obtained, leaving 14-2 per cent, in the megass ; of this 14'2 per cent, 

 the saturated crushing will in the fourth mill extract 10'4 per cent., so that the 

 total extraction is 85 8 -f 104 = 96-2 per cent. Let this 10-4 per cent, 

 contained in the diluted juice be returned to the dry crushed megass ; the 

 immediate effect of this is to reduce the extraction due to dry crushing from 

 85-8 to 85-8 10-4 = 75'4 leaving 24-6 in the megass ; let this megass be 

 crushed to 50 per cent, of fibre ; then of the sugar contained in this megass 

 73-1 per cent, is obtained; -731 x 24*6 = 17'9, so that the extraction at this 

 stage is 75 - 4 + 17'9 = 93*3 and 6*7 is left in the megass, which is now to be 

 saturated with water 30 per cent, on cane, and crushed to 50 per cent, of fibre , 

 of the whole amount of sugar now left in the megass 55'5 per cent, is now 

 extracted; -555 x 6-7 = 3-7, so that the total extraction is 9 3 '3 -f 3*7 = 97*0, 

 Now let the 3*7 per cent, of sugar contained in the fourth mill juice be 

 returned to the dry crushed megass ; the extraction due to dry crushing is 

 now reduced to 85-8 3-7 = 82-1, leaving 17'9 in the megass ; as before 

 73-1 per cent, of this is extracted in the third mill; -731 x 17-9 = 13-1, and 

 the extraction at this stage is 82-1 + 13*1 = 95% leaving 4*8 in the megass ;. 

 again let water 30 per cent, on canes be added and 55-5 per cent, of this is- 

 obtained in the fourth mill ; -555 X 4-8 = 2-7, so that the total extraction is 

 95-2 + 2-7 = 97-9. 



Proceeding in this way and calculating the extraction by a series of steps,, 

 it is found that each successive addition to the extraction becomes smaller and 

 smaller, until no appreciable difference is found. In the present case, the 

 limiting value is found to be practically 98 - 6. If the water had been added 

 in two portions, and the diluted juice had not been returned, the extraction 

 found on similar lines would have been 97-4 per cent. 



For purposes of comparison comparative data of the results to be obtained 

 by different methods of adding the water are given below : 



If canes with 12 per cent, fibre with added water 20 per 

 cent, on canes give in a nine-roller mill with single 

 saturation an extraction of 96-2 



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