330 CHAPTER XVIII 



though attention to this point may open the way to the adoption of the more 

 economical schemes. 



5. The presence of a waste product, bagasse,* which serves as a fuel, 

 ehminates the necessity for the ultimate economy as long as this material 

 affords steam to operate the factory at the maximum efficiency as regards 

 the extraction of sugar. 



Computation of the Steam Consumption. — The steam required in a cane 

 sugar factory will be divided between that used in the engines and that in 

 the heating and evaporation. The greater part of that used in the engines 

 appears again as low pressure steam available for heating and evaporation. 

 With modern engines of the Corliss type, operated at not less than seven 

 atmospheres gauge pressure, and exhausting at half an atmosphere, a 

 consumption of 30 lbs. steam per indicated horse-power-hour is usual. 

 With slide valve engines and lower initial pressures this figure will rise to 

 45 lbs., and in small isolated units a consumption of 60 lbs. may easily be 

 reached. With non-condensing steam turbines of larger (1,000 H.P.) 

 capacity operating at higher pressures and with superheated steam, the 

 consimiption is probably rather greater than that of a Corliss engine. With 

 the smaller units and lower pressures the consumption may rise to 60 lbs. 



Power. — The demand for steam for use in the engines will depend on a 

 number of factors, the most important of which are the number of units 

 in the milling plant, the fibre in the cane, the water supply and the ehmination 

 of small isolated steam-driven units obtained either by intelligent grouping 

 or by the adoption of electric drive. Actual experiment by the writer in 

 a house working up 65 tons of cane per hour with 12 per cent, of fibre gave 

 the following data : — Crusher and 12-roller mill, 87-7 I. H.P. per ton-fibre- 

 hour ; quadruple vacuum pump, 28 I. H.P. ; pan vacuum pumps, 43 I. H.P. ; 

 centrifugals, 72 I. H.P, ; crystallizers, 16 I. H.P. Combining these data 

 with others of record, the following estimate of power consumed can be 

 obtained : — ■ 



Estimate of Power consumed in a Raw Sugar Factory working up 100 short 

 TONS of Cane with it per cent. Fibre per hour in a Crusher and i2-roi.ler Mill, 

 AND with Injection Water pumped to the Condensers, but not circulated 



in a Cooling Tower. 



Indicated Horse-Power. 

 Cane unloading and elevating . . . . . . . . 35 



Milling Plant, including strainers, cush-cush, elevators, etc. 1,000 

 Bagasse conveyors . . . . . . . . . . . . 25 



Boiler feed pump 

 Water supply pump . . 

 Quadruple vacuum pump . . 

 Pan vacuum pumps . . 

 Centrifugals with accessory ge.ir 

 Crystallizers 

 Juice pumps . . 

 Various small pumps 

 Electric light and ice plant 

 Mechanics and carpenters' shop 



50 

 100 



45 

 60 



153 

 25 

 20 



75 

 45 

 20 



1,650 



* The possibility of using bagasse as a paper-making material may in the future alter the correctness of this 

 statement. 



