BAGASSE AS FUEL 



469 



From a study of actual results, and bearing in mind capital, cost of extra 

 fuel, etc., the writer has come to the conclusion that, as a basis of design 

 referred to a cane with 10 per cent, of fibre, the economic limit is reached 

 when about i lb. of bagasse with 50 per cent, fibre is burnt per sq. ft. heating 

 surface per hour. Under these conditions this is equivalent to 400 sq. ft. 

 heating surface per ton-cane-hour, and allowing for one boiler in ten being 

 out of servace for cleaning furnaces, etc., to 450 sq. ft. in round numbers. 

 When the fibre in the cane increases, more bagasse is available for fuel and 

 more will be burnt per sq. ft., with only a small fall in the efficiency, and an 

 increase in the total amount of steam produced, which will be used up in 

 heating a greater amount of mixed juice following on a greater dilution. 

 Some figures from actual factories all of recent des'gn follow : — 



Hawaii. — Thirteen factories. Average 429 : extremes 350 to 570 sq. ft. 

 per ton-cane-hour. 



Java. — Ten factories. Average 429 : extremes 319 to 569 sq. ft. per ton- 

 cane-hour. 



Fig. 284 



Cuba. — Seventeen factories. Average 532 : extremes 385 to 610 sq. ft. 

 per ton-cane-hour. 



In the taking out of these data the results have been expressed as fire-tube 

 heating surface, water-tube heating surface being considered as of 20 per 

 cent, higher value. 



The ratio of grate area to heating surface is found to offer wide variation, 

 the lowest ratio the writer has ever observed being i : 54, and the highest 

 I : 343 ; generally this figure is found to be within the limits i : 70 to i : 120. 

 Connected with this ratio is the quantity of bagasse burnt per sq. ft. of grate 

 area per hour. With a ratio of grate area to heating surface of i : 100, and 

 I lb. bagasse burnt per sq. ft. heating surface per hour, 100 lbs. will be burnt 

 per hour per sq. ft. of grate. 



Of some importance also is the volume of the combustion chamber in 

 relation to fuel burnt. Difficulty at once arises in determining what is the 

 combustion chamber, since some engineers treat the space under the boiler 

 as a combustion chamber, and others only that volume before the gases come 

 in contact with the boiler. Treating of the external furnace only before the 

 gases reach the boiler, the volume usually found is from 10 to 30 cu. ft. per 



