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Abstract(s)
O principal objetivo deste trabalho foi o estudo da combustão de péletes da espécie
invasora Acacia dealbata (Mimosa) e de péletes resultantes de três misturas diferentes de
Acacia dealbata e de Pinus Pinaster (Pinho), para percentagens distintas de cada um dos
elementos, numa caldeira a péletes doméstica.
As amostras da espécie Acacia dealbata foram recolhidas na região de Viseu e depois
cortadas em dimensões menores, para que pudessem ser tratadas posteriormente. Uma estufa
solar foi usada para secar a matéria-prima, até atingir um teor de humidade de,
aproximadamente, 20%. Durante o processo de secagem, aquele valor foi monitorizado.
Após a secagem, as amostras de Acacia foram destroçadas num moinho de navalhas,
Retsch SM100.
Foram produzidos péletes, de Acacia dealbata e das três misturas, com um diâmetro
médio de 6,66 mm, com recurso a uma peletizadora existente no laboratório da ESTGV. O
processo de peletização foi realizado com monitorização de temperatura e pressão.
O processo de combustão dos péletes foi efetuado para três cargas térmicas distintas,
‘carga 1’, ‘carga 3’ e ‘carga 5’, que corresponderam às designações do fabricante da caldeira
para as potências reduzida, média e alta, respetivamente.
Os resultados obtidos, para os diferentes tipos de péletes produzidos, foram comparados
com os resultados obtidos para péletes comerciais de Pinho, certificados através da norma
ENplus.
Determinou-se a eficiência térmica da caldeira, foi avaliada a sua dependência com o
excesso de ar e a emissão de gases de combustão (O2, CO2, CO, NOX) resultantes da combustão
para as diferentes cargas.
Com o aumento da potência térmica da caldeira, foi possível verificar um aumento do
rendimento.
Relativamente às emissões de CO e de NOX, a combustão dos péletes de Acacia dealbata
foi a que apresentou valores mais elevados.
ABSTRACT: The main purpose of this work was the study of combustion of invasive Acacia dealbata pellets, and the three mixtures of Acacia dealbata and Pinus Pinaster pellets, for different percentages of the two species, in a domestic pellets boiler. The samples of Acacia dealbata species were collected in the region of Viseu, and later cut into smaller sizes, so that they could be manageable subsequently. A solar dryer was used to dry the raw material until it had a moisture content of, approximately, 20%. During the drying process, that value was monitored. After drying, Acacia samples were milled in a Retsch SM100, knives type cutting mill. Then, Acacia dealbata and the three mixtures pellets, were produced using a laboratory pelletizer, with an average diameter of 6,66 mm. The process was carried out with temperature and pressure monitoring. The pellet combustion process was carried out for three different thermal loads, ‘load 1’, ‘load 3’ and ‘load 5’, which corresponded to the designations of the boiler manufacturer for the reduced, medium and high power, respectively. The results obtained, for the different types of pellets produced, were compared with the results obtained for commercial Pinus Pinaster pellets, certified by ENplus standard. The thermal efficiency of the boiler was determined, its dependence on excess air evaluated and the emission of combustion gases (O2, CO2, CO, NOX) resulting from the combustion, under the referred different loads. With the increase of the thermal power of the boiler, it was possible to verify an increase in thermal efficiency. Concerning CO and NOX emissions, the combustion of the pellets of Acacia dealbata represented the highest values.
ABSTRACT: The main purpose of this work was the study of combustion of invasive Acacia dealbata pellets, and the three mixtures of Acacia dealbata and Pinus Pinaster pellets, for different percentages of the two species, in a domestic pellets boiler. The samples of Acacia dealbata species were collected in the region of Viseu, and later cut into smaller sizes, so that they could be manageable subsequently. A solar dryer was used to dry the raw material until it had a moisture content of, approximately, 20%. During the drying process, that value was monitored. After drying, Acacia samples were milled in a Retsch SM100, knives type cutting mill. Then, Acacia dealbata and the three mixtures pellets, were produced using a laboratory pelletizer, with an average diameter of 6,66 mm. The process was carried out with temperature and pressure monitoring. The pellet combustion process was carried out for three different thermal loads, ‘load 1’, ‘load 3’ and ‘load 5’, which corresponded to the designations of the boiler manufacturer for the reduced, medium and high power, respectively. The results obtained, for the different types of pellets produced, were compared with the results obtained for commercial Pinus Pinaster pellets, certified by ENplus standard. The thermal efficiency of the boiler was determined, its dependence on excess air evaluated and the emission of combustion gases (O2, CO2, CO, NOX) resulting from the combustion, under the referred different loads. With the increase of the thermal power of the boiler, it was possible to verify an increase in thermal efficiency. Concerning CO and NOX emissions, the combustion of the pellets of Acacia dealbata represented the highest values.
Description
Keywords
Biomassa Bioenergia Combustão Peletização Espécies alternativas