Analytical Techniques - Biomass Gasification, Pyrolysis and Torrefaction - page 447

13.1.3.6 Cellulose
Cellulose is distinguished from extractives by its insolubility in water or
organic solvents, from hemicellulose by its insolubility in aqueous alkaline
solutions, and from lignin by its relative resistance to oxidizing agents and
susceptibility to hydrolysis by acids (Browning, 1967, p. 387; Fengel and
Wegener, 1989).
Cellulose can be measured by isolating it from other components of bio-
mass like, extractive, lignin, and hemicellulose. The following method deter-
mines

the amount of holocellulose, which comprises cellulose and

hemicellulose.
An extractive-free dry sample (2 g) is taken in an extraction thimble. It is
then extracted successively with ethanol benzene for 4 h and with 95% eth-

anol for 4 h in a Soxhlet extractor. The extracted sample is further extracted
with hot water for 3 h in a flask. It is filtered on a fritted glass crucible and
washed with hot water followed by cold water. Suction is applied to the bot-
tom of the crucible to remove excess air. It is then chlorinated by passing
chlorine gas from the inverted funnel on the crucible with fritted glass filter.
The crucible is kept in an ice water bath. After 5 min the suction is released
and cold water is drained. Then the sample is treated twice with hot solution
(75 C) of monoethanolamine (3% in 95% ethanol) for 2 min each time. The
solvent is removed and the wood is washed with ethanol followed by cold
water.
The process of chlorination (3 min) and extraction (2 min) are repeated
until the residue remains white after chlorination and it is no longer colored
by the addition of hot monoethanolamine. The residual substance is weighed
to give the mass of hollocellulose.
The residue is finally washed with alcohol, cold water, and ether and
dried for 2.5 h at 105 C. It is weighed and left in a bottle.

13.1.3.7 Ash
A crucible is cleaned and left in a muffle furnace for a required time to burn
any combustibles. It is then cooled and left in a desiccator. The weighted
mass of the sample is left in the crucible. The crucible is placed in a muffle
furnace at 575 C for several hours to burn off the carbon. After this, the cru-
cible is cooled and weighed. The difference in weight would determine the
amount of ash in the sample.

13.2 HEATING VALUE
The higher heating value (HHV) can be measured in a bomb calorimeter
using ASTM standard D-2015 (withdrawn by ASTM 2000, and not
replaced).