Pyrolysis of wood macrocylinders under pressure: Application of a simple mathematical model

The pyrolysis of wood macrocylinders is studied using a pressurized thermobalance. The experiments carried out on the influence of temperature, pressure and gas velocity show that the pyrolysis appears to be dependent on the temperature, and to a lesser extent on the pressure, which would have an effect on the external heat transfer. An increase in pressure leads to a low augmentation of the decomposition rate and of the yield in charcoal. In the proposed mathematical model, the emission of volatile products is taken into account through the external convective heat transfer.

Wood liquefaction--An overview

During the past decade, numerous papers on wood liquefaction have been published, covering fundamental aspects through to potential processes. After introducing the characteristics of wood, the physico-chemical aspects of wood liquefaction are examined. A large part of the paper is devoted to liquefaction processes: first-generation processes (direct liquefaction), pretreatment processes, usually based on mechano-chemical treatment of lignocellulosic material, and second-generation processes (solvolysis processes).

Pyrolysis of large wood samples

The kinetics of pyrolysis of large wood samples--up to 27 mm--has been studied by isothermal thermogravimetric analysis. Rate of weight loss can be represented by a first order Arrhenius-type equation, with an activation energy of 125 kJ/mole. The temperature inside the wood sample is given by integration of the Fourier law, in which the thermal diffusivity is temperature- and conversion-dependent. This simple model enables one to predict the time needed to achieve pyrolysis of a large wood sample.

Simple mathematical model for the solvolysis of cylindrical pine-wood samples

For producing fuel by the liquefaction of wood, it would be reasonable to use a raw material in the form of large granules instead of sawdust or powder. In this paper, a simple mathematical model, for the solvolysis of wood dowels of various diameters in acidified phenol is described. The modelling is based on a dual diffusion reaction. In order to determine the kinetic constants of the reaction, when the rate is entirely controlled by the chemical reaction, experiments have been carried out on wood powder, well dispersed in the solvent. For the larger pieces of wood, the dissolution appears as a stepwise process. An explanation of this process is given, based on morphological changes in the wood matrix during solvolyis.