Santiago Yubero Jiménez

Particulate matter formation and emission in the combustion of different pulverized biomass fuels

ABSTRACT Particle formation and emission in the combustion of four (orujillo, eucalyptus, oak and chestnut tree) pulverized biomass fuels have been studied. The fuels have been burned in an entrained flow reactor, under controlled and realistic conditions. In all the cases, the final emission distributions contained at least two modes, one of them peaking at 30–200 nm, and the other being in the supermicron range. Alkali sulphates and chlorides account for most of the mass of the fine particles in all cases, while coarse particles essentially retain the inorganic matter properties of the original fuel. K2SO4 is experimentally found to start nucleation over 900°C for orujillo, while KCl is not observed at this temperature. Condensation of KCl on these nuclei is observed in a sample taken at 560°C and in a greater amount at 360°C. The same formation schema was found for the other biomass fuels; the much lower ash content of the latter is thought to cause a “delay” in the onset of these nucleation/condensation steps along the gas cooling process. In spite of these differences, the global similarities observed among the studied fuels confirm the generality of the fine particle formation process in biomass combustion.

Formation and Emission of Submicron Particles in Pulverized Olive Residue (Orujillo) Combustion

The particle formation and emission in the combustion of pulverized olive residue (orujillo) is studied in this work. The fuel has been burned in controlled combustion conditions in an entrained flow reactor. A bimodal distribution with mode peaks at 155 nm and 110 μm is found for fly ashes. Coarse particles have been characterized by laser diffractometry and SEM, while fines have been analyzed by low-pressure impaction, DMA, SEM, and X-ray diffraction. Particles with Dp < 1 μm are composed of only K2SO4 and KCl in the same mass proportion, and possibly K3PO4 (less than 7% in mass). The use of a new particle sampling probe and a TEM allowed a detailed study of the formation of these particles when flue gases cool down. K2SO4 is experimentally found to start nucleation over 900°C, while KCl is not observed at this temperature. Condensation of KCl on these nuclei is observed in a sample taken at 560°C. These “formation steps” are in good agreement with both theoretical calculations by other authors and a simple equilibrium schema shown here.

A comparative study of different methods for the sampling of high temperature combustion aerosols

Three different probes, respectively based on aerodynamic quenching, N2 dilution, and thermophoresis, were used for particle sampling in biomass postcombustion gases from a laboratory reactor at different temperatures (from 1300 to 560°C). The different artifacts caused by the use of each probe were identified and compared. While the classical dilution sampling resulted in the formation (inside the probe) of particles comparable in size and composition to those already existing in the sampled gases, the aerodynamic quenching particle sampling (AQPS) probe always caused the nucleation of vapors into very small (15–20 nm) particles. The difference is attributed to the much higher cooling rate (∼ 108 K/s) at the entrance of the probe. The preliminary results of the thermophoretic probe also reveal significant deviations between the collected sample and the actual particle population in the sampled gas. In general, the results shown here highlight the difficulties in obtaining representative samples in this type of systems, as well as the existence of a variety of possible sampling artifacts, whose interpretation is not straightforward. The AQPS probe is found to provide better results than the other methods considered, and its use might enable the study of both the condensed and vapor phase in hot gases containing important amounts of condensable inorganic vapours.

Los valores sociales en el perfil profesional del trabajador social. Un análisis con estudiantes universitarios

Esta investigacion ha sido subvencionada por el Proyecto de Innovacion Educativa de la Facultad de Trabajo Social (2010/2011), UIE/UCLM.