Lynne Wong's PhD thesis

Bruijn (1963) studied the mass increase of initially dry cane fibre exposed to humid air;
the water adsorbed was reported to be as high as about 40 g per 100 g fibre at room
temperature.
A recent publication on a sorption study of cane rind fibre by Han and Wu (2004)
described the division of sugar cane rind stem with a thickness of 1.0 to 2.0 mm into
segments of 10 to 25 cm in length separated by nodes. The rind stem consisted, on the
cross-section, of an outer wax layer, rind fibres and inner pith. Samples were conditioned
to reach equilibrium at relative humidity,
R
H , values of 32.5, 66, 76, 81 and 93% over
different saturated salt solutions in desiccators. Experimental data of the EMC at various
R
H values were fitted to the sorption isotherm model proposed by Nelson (1983)
⎪⎧
⎨
⎪⎩
⎡ ⎛
⎢ ⎜ −
⎣ ⎝
RT ⎞
m ⎟
w ⎠
EMC = m 1.0 − n
⎜ ⎟ n
( R )
v
1
A
H
⎤
⎥
⎦
⎪⎫
⎬
⎪⎭
where m v is a material constant which approximates the fibre saturation point for
desorption (%), m w is the molar mass of water (18.02 g mol -1 ), R is the universal gas
constant (8.314 J mol -1 K -1 ), T is the absolute temperature (K), and A is the natural
logarithm of the Gibbs free energy per gram of sorbed water as R H approaches zero.
They found that Nelson’s sorption isotherm accurately reproduced the experimental data of
sugar cane rind.
5.4.2 Woody fibre from eucalyptus
In order to design and simulate the pneumatic drying operation of medium density
fibreboard, Moreira et al. (2001) studied eucalyptus fibre to determine the equilibrium
conditions of the fibre with respect to the relative humidity of the air during desorption.
Triplicate samples of fresh fibre (about 0.3 g) were placed in petri-dishes in bottles
containing saturated salt solutions providing a range of relative humidities from 0.07 to
0.91. The bottles were placed in an oven at 70, 55, 40 and 25 °C until equilibrium was
reached (3 – 4 weeks). The equilibrium moisture content was then determined in a vacuum
oven at 70 °C and 0.1 bar.
The sorption isotherms of eucalyptus were found to be of the type II isotherm, and the
three-parameter GAB model was found to fit the experimental data adequately.
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