Flammability behaviour of wood and a review of the methods for its reduction

Wood is one of the most sustainable, aesthetically pleasing and environmentally benign materials. Not only is wood often an integral part of structures, it is also the main source of furnishings found in homes, schools, and offices around the world. The often inevitable hazards of fire make wood a very desirable material for further investigation. As well as ignition resistance and a low heat release rate, timber products have long been required to resist burn-through and maintain structural integrity whilst continuing to provide protection when exposed to fire or heat. Various industry standard tests are thus required to ensure adequate protection from fire is provided. When heated, wood undergoes thermal degradation and combustion to produce gases, vapours, tars and char. In order to understand and alter the fire behaviour of wood, it is necessary to know in as much detail as possible about its processes of decomposition. Various thermal analysis and flammability assessment techniques are utilised for this purpose, including thermogravimetric analysis, cone calorimetry and the single burning item test. The results of such tests are often highly dependent on various parameters including changes to the gas composition, temperature, heating rate, and sample shape size. Potential approaches for fire retarding timber are reviewed, identifying two main approaches: char formation and isolating layers. Other potential approaches are recognised, including the use of inorganic minerals, such as sericrite, and metal foils in combination with intumescent products. Formulations containing silicon, nitrogen and phosphorus have been reported, and efforts to retain silicon in the wood have been successful using micro-layers of silicon dioxide. Nano-scale fire retardants, such as nanocomposite coatings, are considered to provide a new generation of fire retardants, and may have potential for wood. Expandable graphite is identified for use in polymers and has potential for wood provided coating applications are preferred

A laboratory study of the elastic and anelastic properties of the sandstone flooded with supercritical CO2 at seismic frequencies

The paper studies the influence of supercritical CO2 (scCO2) on the elastic and inelastic properties of sandstone at seismic frequencies (0.1 - 100 Hz). The seismic frequency experiments were performed with a low-frequency laboratory apparatus utilizing stress-strain relationship, which was developed to measure the complex Young's moduli of rocks at strain amplitudes from 10-8 to 10-6. The experiments were conducted on water saturated sandstone (Donnybrook, Western Australia) flooded with scCO2. During the experiments with scCO2 the low-frequency system and the pump with scCO2 were held at a temperature of 42° C. The elastic parameters measured for the sandstone with scCO2 at seismic frequencies are close to those obtained for the dry rock. The extensional attenuation was also measured at seismic frequencies for the dry, water saturated and scCO2-injected sandstone. The applicability of Gassmann's theory to saturated scCO2-water mixture was also explored during the experiments

Acoustic response of reservoir sandstones during injection of supercritical CO2

We report experimental results for acoustic response measurements conducted during injection of supercriticalcarbon dioxide into a brine saturated sandstone plug. We measured P- and S-wave velocities (Vp, Vs) as a functionof effective stress and CO2 saturation in a sandstone plug. We demonstrate that Gassmann’s fluid substitutionprocedure matches the experimental results well for this sample. A 3.5% reduction of P-wave velocity after injectionof two pore volumes of CO2 into brine-saturated sample was measured. We conclude that measurement of Vp can beused to estimate CO2 saturations in rock. In addition, x-ray computer tomography (CT) images were acquired atreservoir conditions with a resolution of 33 µm, which provided more detailed information about CO2 saturationsand distributions in the rock. It is envisaged that these techniques (seismic and CT) can be combined in the future toenable a more holistic understanding of how fluid-fluid displacement processes are coupled with the acousticresponse characteristics of the rock

Experimental study of supercritical CO2 injected into water saturated medium rank coal by X-ray microCT

Carbon dioxide geosequestration into deep unmineable coal seams is a technique which can mitigate anthropogenic greenhouse gas emissions. However, coal composition is always complex, and some minerals such as calcite chemically react when exposed to the acidic environment (which is created by scCO2 mixing with formation water). These reactive transport processes are still poorly understood. We thus imaged a water-bearing heterogeneous coal (calcite rich) core before and after scCO2 injection in-situ at high resolutions (3.43 µm) in 3D via X-ray in-situ microCT flooding system. Indeed, the calcite-coal mixed layer was partially dissolved, and absolute porosity and connectivity significantly increased. We thus suggested that such process could be used as an acidizing method in CO2 ECBM. However, such dissolved damage also can significantly affect the rock mechanical properties and potentially induce geohazards

Elastic anisotropy estimation from laboratory measurements of velocity and polarization of quasi-P-waves using laser interferometry

A new method for conducting laboratory measurements of the velocities and polarizations of compressional and shear waves in rock samples uses a laser Doppler interferometer (LDI). LDI can measure the particle velocity of a small (0.03mm2) element of the surface of the sample along the direction of the laser beam. By measuring the particle velocity of the same surface element in three linearly independent directions and then transforming those velocities to Cartesian coordinates, three orthogonal components of the particle-velocity vector are obtained. Thus, LDI can be used as a localized three-component(3C) receiver of ultrasonic waves, and, together with a piezoelectric transducer as a source, it can simulate a 3C seismic experiment in the laboratory. Performing such 3C measurements at various locations on the surface of the sample produces a 3C seismogram, which can be used to separate the P-wave and two S-waves and to find the polarizations and traveltimes of those waves. Then, the elasticity tensor of the medium can be obtained by minimizing the misfit between measured and predicted polarizations and traveltimes. Computation of the polarizations and traveltimes of body waves inside a sample with a given elasticity tensor is based on the Christoffel equation.The predicted polarizations on the surface then are obtained using the anisotropic Zoeppritz equations. The type of velocity measured (phase or group velocity) depends on the acquisition geometry and the material properties. This is taken into account in the inversion procedure. A “walkaway” laboratory experiment demonstrates the high accuracy of this method