J.F. Mastral

Kinetics of pyrolysis of high density polyethylene. Comparison of isothermal and dynamic experiments

Abstract An experimental study of the thermal decomposition of high density polyethylene in an inert atmosphere has been carried out. Both isothermal and dynamic experiments at different heating rates have been performed in a thermobalance. The objective of this work is to analyse the applicability of a simple first-order equation to the prediction of the weight loss of the material, taking into account the complex chain reaction mechanism. The corresponding kinetic parameters have been obtained and its applicability at different heating rates has been analysed. The isoconversion method of Ozawa–Flynn–Wall has been used to obtain the activation energy and the frequency factor from non-isothermal experiments and compare them with the values obtained from isothermal experiments and with the results obtained by other authors.

Kinetic study for the thermal decomposition of cellulose and pine sawdust in an air atmosphere

Abstract Isothermal and dynamic experiments have been performed to obtain kinetic equations for the thermal decomposition of lignocellulosic materials in an air atmosphere. The experiments were performed with cellulose, which is considered to be the main component in these materials, and pine sawdust. Equations corresponding to the different ranges of temperature and solid conversions have been obtained. A comparison has been carried out between the kinetic constant values obtained with cellulose and pine sawdust under the same operating conditions.

Kinetics of the thermal decomposition of polyurethane foams in nitrogen and air atmospheres

Abstract The kinetic equations of polyurethane foam weight loss have been determined and the influence of the atmosphere, using nitrogen and air, has been analyzed. The results of the kinetic constants obtained from isothermal and dynamic experiments have been related. A comparison between the kinetic constant values corresponding to nitrogen and air atmospheres has also been performed. The significance of using the values of solid weight that can be lost at a given temperature is analyzed.

Experimental and theoretical study of the ignition and smoldering of wood including convective effects

Ignition, as one of the most important processes during the initiation and development of a fire, needs to be studied in different situations. In this work, an experimental and theoretical study of the ignition of wood, including convective effects, has been performed. The experimental study includes tests of both spontaneous and piloted ignition with air flows at different velocities over the sample. Depending on the conditions, smoldering was observed, followed either by ignition or extinction. In some cases, decomposition of the sample occurred without the appearance of a flame. A mathematical model has been used that includes the kinetics of thermal decomposition of wood, the latent heat of vaporization of water, and variable thermal properties. The model provided the temperature at each point in the solid, the local conversion of solid, the time to smoldering, and the time to ignition of the material. In general, reasonable agreement between experimental and theoretical results was obtained.

Modelling of the pyrolysis of wet wood

Abstract The influence of moisture content on the thermal decomposition of wood has been analyzed. Using wood slabs, experimental results of temperature profiles and solid conversion for different moisture contents and heat fluxes have been obtained. A mathematical model without adjustable parameters was used to calculate the temperature at different points in the sample and the average total solid conversion. Once the validity of different assumptions of the model had been analyzed, the experimental results were compared with those calculated by the model. Acceptable agreement was achieved.

The influence of the percentage of oxygen in the atmosphere on the thermal decomposition of lignocellulosic materials

Abstract Dynamic experiments with a heating rate of 12 °C min −1 have been carried out for different oxygen concentrations and several types of pine samples. The influence of the initial solid weight and the sample shape on the solid conversion for each oxygen concentration has been analysed. A simple method is proposed to predict the solid conversion for different oxygen concentrations. The kinetic equations corresponding to an air atmosphere are used in this method.

A model for the prediction of the thermal degradation and ignition of wood under constant and variable heat flux

Abstract The ignition of combustible materials is an important aspect of the processes taking place in an unwanted fire. In this work, an experimental and theoretical study of the ignition process of wood has been carried out. Experiments of both spontaneous and piloted ignition have been performed. Constant and decreasing variable heat fluxes have been tested. A mathematical model has been used to predict the time to ignition of wood for the different operating conditions used. The solution of the model provides the temperature at each point of the solid, the local solid conversion and the time to ignition of the material. In general, a good agreement between experimental and theoretical results is obtained.

Thermal decomposition of lignocellulosic materials: comparison of the results obtained in different experimental systems

Abstract An experimental system that allows the use of large particle sizes and the simulation of different operating conditions was built to study the thermal decomposition of lignocellulosic materials. The values of solid conversion and of temperature obtained at different points using spherical particles of pine wood 2 cm in diameter are shown. The conversion values are compared with those calculated from the equations obtained in a thermobalance for small particle sizes.