2.4. Pretreatment severity
Overend and Chornet (1987) initially defined severity parameter
to relate temperature and time for steam explosion pretreatment
based on the assumption that pretreatment effects follow
first-order kinetics and obey the Arrhenius equation. Using this
relationship they defined a reaction ordinate (R0, min) as shown
in Eq. (2):
R0 =
t
·
exp
Tr −
Tb
14.75
(2)
where t is the residence time (min), Tr is the reaction temperature
(◦C), Tb is the base temperature (100 ◦C) and 14.75 is the
conventional energy of activation assuming the overall reaction is
hydrolytic and the overall conversion is first order. The logarithm of
the reaction ordinate defines the severity during steam explosion
pretreatment such that severity is equal to log(R0).
A modified severity parameter was later developed by Chum
et al. (1990) for use with sulfuric acid pretreatment was shown in
Eq. (3):
M0 =
t
·
Cn ·
exp
Tr −
Tb
14.75
(