Delignification Kinetics Models H Factor Model. Provides mills with the ability to handle common disturbance such as inconsistent digester heating and cooking time variation. 170. 900. 700. 130. Relative Reaction Rate. 500. H factor equal to area under this curve. Temperature °C. 300.
Relative Reaction Rate
H factor equal
to area under this
Hours from StartDelignification Kinetics ModelsH Factor/Temperature
k0 is such that H(1 hr, 373°K) = 1
Relative reaction rate
k = Function of [HS-] and [OH-]
T [=] °K
Kappa (or yield) = -(log(H)*EAn)
,, and n are parameters that must be fit to the data. Values of ,, and n for kappa prediction are shown in the table below.
Warning: These are empirical equations and apply only over the specified kappa range. Extrapolation out of this range is dangerous!
Functional relationship between L and [OH-]
Slopes of lines are not a function of EA charge
Model can handle effect of main disturbances on pulping kinetics
For softwood: Initial to bulk ~ 22.5% on wood
Bulk to residual ~ 2.2% on wood
Pulping data for thin chips – Gullichsen’s data
Pulping data for mill chips - Gullichsen’s data
Model works well until very low lignin content
Modeling yield prediction – A Very Difficult Modeling Problem
Basic Structure: dc/dt=k*dL/dt
Some physical justification for this is given by carbohydrate-lignin linkages.
Carbohydrates lumped into a single group.
Dependence of viscosity on pulping conditions was modeled
Gullichsen data on mill chips