Kinetic study of the secondary thermal decomposition of Kraft lignin

The kinetics of the thermal decomposition of Kraft lignin were studied in a system comprising an association of two reactors connected in series. In the first reactor, a Pyroprobe 1000, the primary reactions take place and the extension of secondary reactions can be considered negligible. The Pyroprobe 1000 is connected to a tubular reactor (secondary reactor) in which secondary thermal reactions take place. To study the secondary reactions, a model of the hydrodynamics in the reactor is needed. The residence time distribution, together with a dispersion model in a system of non-isothermal flow, are considered. Variations of the dispersion coefficient with temperature are taken into account. The overall secondary reaction is studied admitting first order kinetics. The model also takes into account the variation of the primary reactions with temperature and time. For the primary thermal decomposition of Kraft lignin, the kinetic parameters obtained with a Pyroprobe 1000 were considered.