Juan de Dios Rivera

Flammability and the Heat of Combustion of Natural Fuels: A Review

Heat of combustion (HoC) is a key characteristic of fuels when analyzing and modeling wildfire scenarios. Despite significant differences in the structure of fuels from different environments, HoC is frequently considered a constant. This article briefly reviews methods used to describe natural fuels and the various different definitions of HoC. We also summarize measured values of HoC and elemental analyses of 238 plant genera reported in 28 papers since 1973. A statistical analysis of these data provided mean values and standard deviations of HoC for fuels according to six broad plant functional groups. Permutational Multivariate Analysis of Variance (PERMANOVA) demonstrated significant differences in the HoC with ground fuels and softwoods having particularly high values. Net heat of combustion was calculated for four fuel groups and the tabulated data may help to improve wildfire modeling and highlights fuels where further measurements of HoC are required.

MEASUREMENT OF FLAME SPEED IN COPPER CONCENTRATE CLOUDS

More than 50% of the world primary copper is produced by Flash Smelting technology [1], which partially burns copper concentrate particles. It has proved to be superior to other processes because of its low fuel consumption, reduced fugitive-emissions and high production rate. Despite of all these advantages, Flash Smelting presents some operational problems, the most important being the control of magnetite formation and dust loss in the off-gases. The control of these variables is difficult due to poor understanding of the complex interactions between the processes involved, such as thermodynamics, chemical kinetics, mass and heat transfer, local distribution of oxygen concentration, and fluid-flow conditions. One practical tool to understand these complex interactions is the study of flame propagation in the Copper Concentrate (CC) cloud. In this work we developed an experimental method to estimate the velocity of the flame propagation in a CC cloud. We performed measurements in a vertical burner using rich mixtures, which showed that flame speed is inversely proportional to particle size and CC concentration. Also, the flame speed is mainly a function CC/oxygen mass ratio, independent of the oxygen dilution in the gas. In this moment, as a second part of this investigation, we are developing a mathematical model to predict flame speeds of the same order of magnitude and trend as the ones measured experimentally. The model includes heat generation and all modes of heat transfer i.e. conduction, convection, and radiation

Laboratorio de Ensayo de Resistencia al Fuego

Although fire statistics in Chile are not very complete, those available clearly show that fire losses have grown significantly in the last few years. Insurance reports indicate that fire related claims have grown almost three fold between 1989 and 1997 (from 6 to more than 17 million dollars [1]). This significant increase in losses can be attributed to many factors of which one of great importance is the dramatic change in construction practices in Chile. Among the changes are a significant increase in construction volume, industrial growth, development of local construction methods and technology and an increasing preference for taller and larger buildings. As an example it can be stated that 23 out of the 25 tallest buildings in Santiago were built within the last 10 years [2]. Despite this dramatic change, Chilean codes and standards have remained almost unaltered throughout the same period[3]. Furthermore, training and education in the area of fire safety is restricted to the fire service and a few occasional training courses. Fire safety authorities and practitioners generally fulfill their roles with simply an intuitive knowledge of current technology and practices. It is therefore clear that a dramatic influx of technology into fire safety practices is necessary in Chile. It is within this framework that the “Laboratorio de Ensayo de Resistencia al Fuego” was developed at the Pontificia Universidad Catolica de Chile. The laboratory is a joint venture between the Department of Mechanical and Metallurgical Engineering and the Department of Construction Management and Engineering. The Chilean Government collaborated through the Fund for Development and Innovation (Fondo para el Desarrollo e Innovacion (FDI-CORFO)). The University and the Ministry of Housing and Urbanism provided significant matching funds. The laboratory officially opened in May 2002. The first stage of development has emphasized the construction of equipment that conforms to Chilean standards that require certification for fire resistance and material flammability. A single oven that allows for testing for fire resistance of horizontal and Copyright