Sergio Nogales

A Review of Pellets from Different Sources

The rise in pellet consumption has resulted in a wider variety of materials for pellet manufacture. Thus, pellet industry has started looking for alternative products, such as wastes from agricultural activities, forestry and related industries, along with the combination thereof, obtaining a broad range of these products. In addition, the entry into force of EN ISO 17225 standard makes wood pellet market (among other types) possible for industry and household purposes. Therefore, wastes that are suitable for biomass use have recently increased. In this study, the main characteristics of ten kinds of laboratory-made pellets from different raw materials were analyzed. Thus, we have focused on the most limiting factors of quality standards that determine the suitability for biomass market, depending on the kind of pellet. The results showed considerable differences among the analyzed pellets, exceeding the limits established by the standard in almost all cases, especially concerning ash content and N and S composition. The requirements of the studied standard, very demanding for certain factors, disable the entry of these densified wastes in greater added value markets.

An Incremental Mori-Tanaka Homogenization Scheme for Finite Strain Thermoelastoplasticity of MMCs

The present paper aims at computational simulations of particle reinforced Metal Matrix Composites as well as parts and specimens made thereof. An incremental Mori-Tanaka approach with isotropization of the matrix tangent operator is adopted. It is extended to account for large strains by means of co-rotational Cauchy stresses and logarithmic strains and is implemented into Finite Element Method software as constitutive material law. Periodic unit cell predictions in the finite strain regime are used to verify the analytical approach with respect to non-proportional loading scenarios and assumptions concerning finite strain localization. The response of parts made of Metal Matrix Composites is predicted by a multiscale approach based on these two micromechanical methods. Results for the mesoscopic stress and strain fields as well as the microfields are presented to demonstrate to capabilities of the developed methods.

Analysis of Pelletizing of Granulometric Separation Powder from Cork Industries

Cork industries generate a considerable amount of solid waste during their processing. Its management implies a problem for companies that should reconsider its reuse for other purposes. In this work, an analysis of pelletizing of granulometric separation powder, which is one of the major wastes in cork industries and which presents suitable properties (as an raw material) for its thermal use, is studied. However, its characteristic heterogeneity, along with its low bulk density (which makes its storage and transportation difficult) are restrictive factors for its energy use. Therefore, its densified form is a real alternative in order to make the product uniform and guarantee its proper use in boiler systems. Thus, the cork pellets (from granulometric separation powder) in the study met, except for ash content specification, the specifications in standard European Norm EN-Plus (B) for its application as fuel for domestic use.

Forming Simulations of MMC Components by a Micromechanics Based Hierarchical FEM Approach

The present work deals with computational simulations of an elastoplastic particulate metal matrix composite undergoing finite strains. Two different approaches are utilized for homogenization and localization; an analytical constitutive material law based on a mean field approach, and a periodic unit cell method. Investigations are performed on different length scales. The Finite Element Method is employed to predict the macroscopic response of a component made from a metal matrix composite. Its constitutive material law, based on the incremental Mori Tanaka approach, has been implemented into an Finite Element Method package, and is extended to the finite strain regime. This approach gives access to the mesoscale fields as well as to approximations for the microscale fields in the individual phases of the composite. Selected locations within the macroscopic model are chosen and their entire mesoscopic deformation history is applied to unit cells using the periodic microfield approach. As a result, mesos...

Control of Several Emissions during Olive Pomace Thermal Degradation

Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25–750 °C and a heating rate of 20 °C·min−1. The following species were analysed: aromatic compounds (benzene and toluene), sulphur emissions (sulphur dioxide), 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor.

Continuum Modeling of Diffusive Transport in Inhomogeneous Solids

General features of homogenization and localization in studying the conduction behavior of inhomogeneous materials are introduced and two groups of methods for solving such problems are presented. First, mean field and bounding approaches are discussed and comparisons between the predictions of relevant methods are given. Next, modeling approaches to studying discrete microstructures are covered, the main emphasis being put on periodic homogenization and windowing procedures. Finally, an application of the methods to diamond particle reinforced aluminum is presented, in which interfacial effects play an important role.