BAGASSE AS FUEL 455 



more carbon than the latter. Thus Xorris found ^vith Yellow Caledonia 

 cane 48-75 per cent, carbon in the rind fibre and 47-2 per cent, in the pith 

 fibre. So also as between varieties which differ in the proportion of rind 

 and pith tissue differences may be expected, but these differences are not 

 of much moment, and it is justifiable to accept a flat rate for the composition 

 of dry bagasse. Including the ash in certain computations that follow, this 

 will be taken as 46-5 per cent, carbon, 6-5 per cent. h3-drogen, and 46-0 

 per cent, oxygen. 



Heat of Combustion of Bagasse.— As dry bagasse of any origin has nearly 

 the same ultimate composition, it would be expected that its heat of combus- 

 tion would also vary within very narrow limits. That this is so has been 

 definitely proved bv the determinations of Geerligs,^ who found values from 

 8289 to 8514 B.T.U. per lb. of dry bagasse ; of Burwell,^ 8289 to 8384 ; 

 of Norris,' 8089 to 8344 ; and of Kerr,^ 8375. The differences that occur 

 may reasonabl}- be attributed to variation in the proportion of rind tissue 

 and pith tissue. Xorris found the former to afford 4 per cent, more heat 

 than the latter, and this difference may also be extended to give the bagasse 

 from one variety a higher value than that from another. In the various 

 computations that follow the heat of combustion of dry bagasse will be uni- 

 formly taken as 8350 B.T.U. per lb. This figure is considerably higher 

 than that obtained by calculation from the heats of combustion of the fibre 

 (taken as cellulose) and of the sugars, or as obtained from Welter's rule, 

 which gives the heat of combustion of an organic compound as that of its 

 constituents, less that of such hydrogen present which can be combined 

 with oxygen in the proportions in which they form water. 



Products of Combustion of Bagasse. — One pound of carbon requires for 

 its combustion 2 • 67 lbs. oxygen, and one pound of hydrogen requires 7 • 93 

 lbs. oxygen. One pound of dry bagasse of the typical composition accepted 

 above will then require : 0-465 X 2-67 + 0-065 X 7-93 = 1-75 lbs. oxygen. 

 The bagasse itself contains 0-45 lb. oxygen, so that there has to be supplied 

 I - 30 lb. from the air. 



The composition of the atmosphere will be taken as oxygen 23 per cent., 

 water vapour i per cent., nitrogen 76 per cent., included in " nitrogen " 

 being aU the rarer gases of the atmosphere. 



To supply 1-30 lb. in oxygen there will be then required 5-65 lbs. air, 

 and the products of combustion per pound of bagasse will be : — 



Due to carbon o -465 x 2 -67 -|- o -465 . . i -70 lb. Carbon dioxide. 



Due to hydrogen o -065 x 7 -93 -|- o -065 . . 0-58 lb. Water. 



Introduced with air 5-65 X o -oi .. o -06 lb. 



5-65 X 0-76 .. 4 -30 lb. Nitrogen. 



It is not possible to burn anj- material with the admission of only the exact 

 amount of air necessary ; for, with the ver^^ best control, 50 per cent, 

 excess is necessary, and 100 per cent, excess is not considered unreason- 

 able. With 50 per cent., 75 per cent., and 100 per cent, excess air, the 

 products of combustion per pound of dry bagasse will then be : — 



