Formation and Control of Trace Metal Emissions in Co-Firing of Biomass, Peat, and Wastes in Fluidised Bed Combustors

Environmentally harmful consequences of fossil fuel utilisation andthe landfilling of wastes have increased the interest among the energy producers to consider the use of alternative fuels like wood fuels and Refuse-Derived Fuels, RDFs. The fluidised bed technology that allows the flexible use of a variety of different fuels is commonly used at small- and medium-sized power plants ofmunicipalities and industry in Finland. Since there is only one mass-burn plantcurrently in operation in the country and no intention to build new ones, the co-firing of pre-processed wastes in fluidised bed boilers has become the most generally applied waste-to-energy concept in Finland. The recently validated EU Directive on Incineration of Wastes aims to mitigate environmentally harmful pollutants of waste incineration and co-incineration of wastes with conventional fuels. Apart from gaseous flue gas pollutants and dust, the emissions of toxic tracemetals are limited. The implementation of the Directive's restrictions in the Finnish legislation is assumed to limit the co-firing of waste fuels, due to the insufficient reduction of the regulated air pollutants in the existing flue gas cleaning devices. Trace metals emission formation and reduction in the ESP, the condensing wet scrubber, the fabric filter, and the humidification reactor were studied, experimentally, in full- and pilot-scale combustors utilising the bubbling fluidised bed technology, and, theoretically, by means of reactor model calculations. The core of the model is a thermodynamic equilibrium analysis. The experiments were carried out with wood chips, sawdust, and peat, and their refuse-derived fuel, RDF, blends. In all, ten different fuels or fuel blends were tested. Relatively high concentrations of trace metals in RDFs compared to the concentrations of these metals in wood fuels increased the trace metal concentrations in the flue gas after the boiler ten- to hundred-folds, when RDF was co-fired with sawdust in a full-scale BFB boiler. In the case of peat, lesser increase in trace metal concentrations was observed, due to the higher initial trace metal concentrations of peat compared to sawdust. Despite the high removal rate of most of the trace metals in the ESP, the Directive emission limits for trace metals were exceeded in each of the RDF co-firing tests. The dominat trace metals in fluegas after the ESP were Cu, Pb and Mn. In the condensing wet scrubber, the flue gas trace metal emissions were reduced below the Directive emission limits, whenRDF pellet was used as a co-firing fuel together with sawdust and peat. High chlorine content of the RDFs enhanced the mercuric chloride formation and hence the mercury removal in the ESP and scrubber. Mercury emissions were lower than theDirective emission limit for total Hg, 0.05 mg/Nm3, in all full-scale co-firingtests already in the flue gas after the ESP. The pilot-scale experiments with aBFB combustor equipped with a fabric filter revealed that the fabric filter alone is able to reduce the trace metal concentrations, including mercury, in the flue gas during the RDF co-firing approximately to the same level as they are during the wood chip firing. Lower trace metal emissions than the Directive limits were easily reached even with a 40% thermal share of RDF co-firing with sawdust.Enrichment of trace metals in the submicron fly ash particle fraction because of RDF co-firing was not observed in the test runs where sawdust was used as the main fuel. The combustion of RDF pellets with peat caused an enrichment of As, Cd, Co, Pb, Sb, and V in the submicron particle mode. Accumulation and release oftrace metals in the bed material was examined by means of a bed material analysis, mass balance calculations and a reactor model. Lead, zinc and copper were found to have a tendency to be accumulated in the bed material but also to have a tendency to be released from the bed material into the combustion gases, if the combustion conditions were changed. The concentration of the trace metal in the combustion gases of the bubbling fluidised bed boiler was found to be a summary of trace metal fluxes from three main sources. They were (1) the trace metal flux from the burning fuel particle (2) the trace metal flux from the ash in the bed, and (3) the trace metal flux from the active alkali metal layer on the sand (and ash) particles in the bed. The amount of chlorine in the system, the combustion temperature, the fuel ash composition and the saturation state of the bed material in regard to trace metals were discovered to be key factors affecting therelease process. During the co-firing of waste fuels with variable amounts of e.g. ash and chlorine, it is extremely important to consider the possible ongoingaccumulation and/or release of the trace metals in the bed, when determining the flue gas trace metal emissions. If the state of the combustion process in regard to trace metals accumulation and/or release in the bed material is not known,it may happen that emissions from the bed material rather than the combustion of the fuel in question are measured and reported.

La nueva formación del profesorado en Francia: la experiencia del I.U.F.M. de la Académie de Grenoble

Se describen las características de la formación inicial de los profesores en Francia a partir del análisis del funcionamiento organizativo y del plan de estudios desarrollado en el Institut Universitaire de Formation des Maîtres de la Académie de Grenoble, y se comparan algunos de los rasgos definitorios del nuevo modelo francés de formación del profesorado con la configuración que ha ido adquiriendo ésta en nuestro país, así como con los cambios institucionales y de planes de estudios que aquí se han venido gestando durante estos últimos años.

The representation of EFL teachers’ views on the role of English as a Lingua Franca

El creciente número de hablantes no nativos de inglés en el mundo constituye la base a partir de la cual se han hecho recientes afirmaciones alrededor de la necesidad de enfatizar el papel del inglés como lingua franca en las clases de inglés. Este artículo investiga la visión de los profesores catalanes de inglés al respecto mediante un cuestionario centrado en aspectos como la preferencia de profesores nativos o no nativos, el conocimiento cultural idóneo para el profeso- rado de inglés, y la variedad de inglés escogida. Los resultados indican que el profesorado está influido por la supremacía del hablante nativo y una visión del inglés todavía restringida a las comunidades de hablantes nativos, con algunas diferencias significativas encontradas entre distintos grupos de profesores.

Non-native English-speaking English language teachers: history and research

Although the majority of English language teachers worldwide are non-native English speakers, no research was conducted on these teachers until recently. After the pioneering work of Robert Phillipson in 1992 and Peter Medgyes in 1994, nearly a decade had to elapse for more research to emerge on the issues relating to non-native English teachers. The publication in 1999 of George Braine's book Nonnative educators in English language teaching appears to have encouraged a number of graduate students and scholars to research this issue, with topics ranging from teachers' perceptions of their own identity to students' views and aspects of teacher education. This article compiles, classifies, and examines research conducted in the last two decades on this topic, placing a special emphasis on World Englishes concerns, methods of investigation, and areas in need of further attention.

Wikis e innovación docente

El Espacio Europeo de Educación Superior exige un cambio en las metodologías docentes tradicionales que las nuevas tecnologías pueden favorecer. La Web 2.0 ofrece gran variedad de posibilidades para hacer del estudiante un agente activo en el proceso de aprendizaje, pero es la tecnología wiki la que parece adaptarse mejor a las nuevas necesidades docentes, como son la consideración de una serie de competencias genéricas para la formación integral del alumno que van más allá de los meros conocimientos específicos de una asignatura. Los profesores universitarios están empezando a experimentar con wikis en sus asignaturas, pero el apoyo institucional que reciben no parece suficiente para que el uso de esta herramienta se generalice en toda la universidad.

Intervention de la pensée représentative de futurs enseignant-e-s dans leurs prises de position envers l'intégration scolaire

In the past two decades, international recommendations have made inclusive education a priority issue. Many countries have adopted school policies inciting players to question their representations about the duties and purposes of schooling and their role therein. In Switzerland, a new national and cantonal framework defines the integration of students with disabilities or special educational needs in the regular classroom as a priority. However, progress in this area is modest and many researchers are left wondering how teachers could be better prepared to meet the special needs of some students. Initial training is thus seen as essential in bringing pre-service teachers to develop open attitudes toward students with disabilities or special educational needs. While many studies have examined the role of training in building professional attitudes, very few deal with teacher representations of inclusive education, let alone those of future teachers. Our research focuses on two samples of pre-service teachers in the beginning, middle or end of their initial training. 261 pre-service teachers for primary education and 212 pre-service teachers for secondaiy education are involved in the study. The research aims to highlight the role of their representative thinking in building their attitudes towards inclusive education. Our results show that objectification remains essentialist and focuses on the prototypes of the most publicized disabilities. They also showed the weakness of the training system as perceived by future teachers. Even though they have maintained or strengthened positive attitudes towards integration, most leave their training with a reinforced sense of apprehension when faced with the disabilities or special educational needs that they expect to encounter in their future work. Although pre-service teachers consider their training insufficient, it nevertheless positively influences their attitudes toward integration. In particular, greater internship practice, however modest it may be, has a significant effect on attitudes of future teachers by increasing their perception of competence and confidence. -- Ces deux dernières décennies, les recommandations internationales ont fait de l'inclusion scolaire une thématique prioritaire. De nombreux pays ont adopté des politiques scolaires obligeant les acteurs scolaires à interroger leurs représentations des missions de l'école et leur rôle au sein de celle-ci. En Suisse, un nouveau cadre national et cantonal a défini comme prioritaire l'intégration dans l'école ordinaire des élèves en situation de handicap ou ayant des besoins éducatifs particuliers. Or, les avancées en la matière restent modestes et de nombreux chercheurs se questionnent sur la manière dont les enseignant-e-s pourraient être mieux préparés à répondre aux besoins éducatifs particuliers de certains élèves. La formation initiale est ainsi perçue comme essentielle pour amener les futurs enseignant-e-s pour développer des attitudes ouvertes envers les élèves en situation de handicap ou ayant des besoins éducatifs particuliers. Si beaucoup d'études portent sur le rôle de la formation dans la construction d'attitudes professionnelles, très peu traitent des représentations des enseignant-e-s à l'égard de l'intégration scolaire et encore moins de celles des futurs enseignant-e-s. Notre recherche porte sur deux populations de futurs enseignant-e-s en début, au milieu ou en fin de formation. Elles sont composées respectivement de 261 étudiant-e-s se destinant à l'enseignement primaire et de 212 étudiant-e-s se destinant à l'enseignement secondaire. La recherche vise à mettre en évidence l'intervention de leur pensée représentative dans leurs prises de position envers l'intégration scolaire. Nos résultats montrent que l'objectivation reste essentialiste et se focalise sur les prototypes de situations de handicap les plus médiatisés. Nos résultats font également fait apparaître la faiblesse du dispositif de formation tel que perçu les futurs enseignant-e-s. Quand bien même ont-ils conservé ou renforcé des attitudes favorables à l'intégration, ils quittent pour la plupart leur formation avec une appréhension renforcée à l'égard des situations de handicap ou de besoins éducatifs particuliers qu'ils s'attendent à rencontrer dans leur future pratique. Bien que la formation soit jugée insuffisante par les étudiant-e-s, elle oriente néanmoins favorablement leurs prises de position envers l'intégration des élèves concernés. En particulier, une plus grande pratique de stage, si modeste soit-elle, a un effet important sur ces prises de position par l'augmentation du sentiment de compétence et la perception d'assurance des futurs enseignant-e-s.