That is, the moisture in a juice containing 12 per cent of sugar will be evaporated by the heat developed by the combustion of the contained sugar. It would, therefore, appear that a bagasse containing such juice has a calorific value due only to its fiber content. This is, of course, true only where the highest products of oxidization are formed during the combustion of the organic matter. This is not strictly the case, especially with a bagasse of a high moisture content which will not burn properly but which smoulders and produces a large quantity of products of destructive distillation, chiefly heavy hydrocarbons, which escape unburnt. The reasoning, however, is sufficient to explain the steam making properties of bagasse of a low sucrose content, such as are secured in Java, as when the sucrose content is lower, the heat value is increased by extracting more juice, and hence more sugar from it. The sugar operations in Java exemplify this and show that with a high dilution by maceration and heavy pressure the bagasse meets all of the steam requirements of the mills without auxiliary fuel.
A high percentage of silica or salts in bagasse has sometimes been ascribed as the reason for the tendency to smoulder in certain cases of soft fiber bagasse. This, however, is due to the large moisture content of the sample resulting directly from the nature of the cane. Soluble salts in the bagasse has also been given as the explanation of such smouldering action of the fire, but here too the explanation lies solely in the high moisture content, this resulting in the development of only sufficient heat to evaporate the moisture.
[TABLE 43] ANALYSES AND CALORIFIC VALUES OF BAGASSE
Source
Moisture
C
H
O
N
Ash
B. t. u. per Pound Dry Bagasse
Cuba
51.50
43.15
6.00
47.95
…
2.90
7985
Cuba
49.10
43.74
6.08
48.61
…
1.57
8300
Cuba
42.50
43.61
6.06
48.45
…
1.88
8240
Cuba
51.61
46.80
5.34
46.35
…
1.51
…
Cuba
52.80
46.78
5.74
45.38
…
2.10
…
Porto Rico
41.60
44.28
6.66
47.10
0.41
1.35
8359
Porto Rico
43.50
44.21
6.31
47.72
0.41
1.35
8386
Porto Rico
44.20
44.92
6.27
46.50
0.41
1.90
8380
Louisiana
52.10
…
…
…
…
2.27
8230
Louisiana
54.00
…
…
…
…
…
8370
Louisiana
51.80
…
…
…
…
…
8371
Java
…
46.03
6.56
45.55
0.18
1.68
8681
[Table 43] gives the analyses and heat values of bagasse from various localities. [Table 44] gives the value of mill bagasse at different extractions, which data may be of [Pg 207] service in making approximations as to its fuel value as compared with that of other fuels.
[TABLE 44] ANALYSES AND CALORIFIC VALUES OF BAGASSE
Per Cent Extraction of Weight of Cane
Per Cent Moisture in Bagasse
Fiber
Sugar
Molasses
B. t. u. Value per Pound of Bagasse
Pounds of Bagasse Equivalent to one Pound of Coal of 14,000 B. t. u.
BASED UPON CANE OF 12 PER CENT FIBER AND JUICE CONTAINING 18 PER CENT OF SOLID MATTER. REPRESENTING TROPICAL CONDITIONS
75
42.64
48.00
3996
6.24
451
3.12
217
4664
525
4139
3.38
77
39.22
52.17
4343
5.74
414
2.87
200
4958
483
4475
3.13
79
35.15
57.14
4757
5.14
371
2.57
179
5307
433
4874
2.87
81
30.21
63.16
5258
4.42
319
2.21
154
5731
372
5359
2.61
83
24.12
70.59
5877
3.53
256
1.76
122
6255
297
5958
2.35
85
16.20
80.00
6660
2.40
173
1.20
83
6916
200
6716
2.08
BASED UPON CANE OF 10 PER CENT FIBER AND JUICE CONTAINING 15 PER CENT OF SOLID MATTER. REPRESENTING LOUISIANA CONDITIONS
75
51.00
40.00
3330
6.00
433
3.00
209
3972
678
3294
4.25
77
48.07
43.45
3617
5.66
409
2.82
196
4222
592
3630
3.86
79
44.52
47.62
3964
5.24
378
2.62
182
4524
548
3976
3.52
81
40.18
52.63
4381
4.73
342
2.36
164
4887
495
4392
3.19
83
35.00
58.82
4897
4.12
298
2.06
143
5436
431
5005
2.80
85
28.33
66.67
5550
3.33
241
1.67
116
5907
349
5558
2.52
Furnace Design and the Combustion of Bagasse —With the advance in sugar manufacture there came, as described, a decrease in the amount of bagasse available for fuel. As the general efficiency of a plant of this description is measured by the amount of auxiliary fuel required per ton of cane, the relative importance of the furnace design for the burning of this fuel is apparent.
In modern practice, under certain conditions of mill operation, and with bagasse of certain physical properties, the bagasse available from the cane ground will meet the total steam requirements of the plant as a whole; such conditions prevail, as described, in Java. In the United States, Cuba, Porto Rico and like countries, however, auxiliary fuel is almost universally a necessity. The amount will vary, depending to a great extent upon the proportion of fiber in the cane, which varies widely with the locality and with the age at which it is cut, and to a lesser extent upon the degree of purity of the manufactured sugar, the use of the maceration water and the efficiency of the mill apparatus as a whole.
