PHENOMENOLOGICAL KINETICS OF WOOD DELIGNIFICATION - APPLICATION OF A TIME-DEPENDENT RATE-CONSTANT AND A GENERALIZED SEVERITY PARAMETER TO PULPING AND CORRELATION OF PULP PROPERTIES

Kraft delignification kinetics has been modelled on the basis of a fir st order decay process with a time-dependent rate constant. A generali zed severity parameter derived from this kinetic model, R(OH), has bee n applied to describe the lignin solubilization during alkaline (soda and Kraft) and bisulphite pulping of different wood species. The model has been succesfuly applied to data sets available from the literatur e. Our approach has combined the main process variables (temperature, time and chemical load) into a single parameter, R(OH), which is then used as a reaction ordinate to map the changes in chemical composition and physical properties. An extension of the initial formulation of t he R(OH) parameter has been made to cover the situations where the cat alytic system is composed by two active chemical species, as in the Kr aft process.