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Abstract(s)
A presente dissertação foi realizada no âmbito da Unidade Curricular Dissertação/ Projecto/Estágio, que se enquadra no plano de estudos do Mestrado em Energias Sustentáveis, lecionado no Instituto Superior de Engenharia do Porto (ISEP). Este trabalho integra-se no projeto de mobilização de biomassa de podas para valorização energética desenvolvido no centro para a valorização de resíduos (CVR), em parceria com outros centros de investigação portugueses e espanhóis para promover a produção de novos biocombustíveis. Os resíduos florestais e de jardim representam fontes de biomassa lenho-celulósica com potencial interesse para a produção de combustível derivado de resíduos compactado (CRDc) que posteriormente pode ser usado quer para produzir energia em caldeiras, quer para produzir biochar e bio-óleo em sistemas de pirólise. A combustão em caldeiras obriga à utilização de CRDc certificado e em conformidade com as exigências legais, nomeadamente no que respeita aos teores de humidade e de cinzas, e ao poder calorífico. Também a presença de outros contaminantes está fortemente limitada, tendo em vista a garantia dos valores-limite de emissão (VLE) das emissões gasosas. Assim, configura-se como pertinente o estudo da viabilidade de valorização deste tipo de resíduos. Os objetivos do presente trabalho recaíram especificamente sobre a vertente do estudo das emissões dos gases de combustão de uma caldeira alimentada com diversos tipos de combustíveis sólidos. Para esta vertente, foram utilizados briquetes comerciais (serrim) e briquetes provenientes de podas de biomassa, ambos os briquetes foram produzidos no CVR a partir de resíduos de biomassa florestal como serrim de pinho, poda de videira, poda de kiwi, poda de macieira, poda de oliveira e poda urbana. Para concretizar estes objetivos, procedeu-se à montagem da instalação experimental que, para além da caldeira, inclui vários componentes utilizados nas medições ao longo dos ensaios. Numa primeira fase do trabalho foram realizados estudos nas biomassas acima descritas para obter um conhecimento sobre as biomassas. Esses estudos passaram pela determinação do teor de humidade, teor de cinzas, matéria volátil, carbono fixo, podercalorífico e análise elementar dos combustíveis em estudo. No que diz respeito ao teor de humidade os valores variam entre os 9,5 e 19,5 % de humidade (poda urbana e poda de kiwi respetivamente), o teor de cinzas apresentam resultados entre os 0,8 e 5,1 % (serrim e poda de macieira), a matéria volátil apresentam valores entre os 78,7 e 83,7 % (poda de oliveira e serrim), no que diz respeito ao carbono fixo os valores variam na casa dos 15,5 e 17,6 % (serrim e podas de oliveira respetivamente), em relação ao poder calorífico inferior os valores variam entre os 14,7 e 18,6 MJ/kg (poda de macieira e serrim respetivamente) em contraste com os valores do poder calorífico superior que demonstram valores que oscilam entre os 15,8 e 18,6 MJ/kg (poda de macieira e poda de kiwi). Com este estudo realizado foi dado início à produção dos briquetes para a realização da combustão dos mesmos na caldeira. De seguida, foi criada um formulário de ensaio dos briquetes produzidos consoante a matéria-prima utilizada na sua produção. Assim a humidade, comprimento, massa, massa volúmica e área de secção foram fatores presentes nessa ficha. É de salientar que todos os briquetes produzidos na briquetadora foram concebidos da mesma maneira. Seguidamente a atenção recaiu na vertente principal deste trabalho, a valorização de resíduos de biomassa pelo meio da combustão. Os ensaios realizados, foram divididos em três partes distintas: na primeira parte avaliou-se a caracterização do combustível sólido, ou seja, o caudal mássico do combustível, temperaturas, velocidade de escoamento, densidade, entre outros, considerando condições aproximadas de regime permanente. Na segunda etapa foi analisada a composição dos gases de combustão (𝑂2 , 𝐶𝑂2, 𝑁2 e 𝐻2𝑂). Por fim foram monitorizadas as emissões poluentes resultantes dos gases de combustão (CO, 𝑁𝑂𝑥, 𝑃𝑎𝑟𝑡í𝑐𝑢𝑙𝑎𝑠, 𝑒 𝐶𝑂𝑇), observando-se maior emissão de CO no ensaio com briquetes de serrim (989 mg/𝑚3 @ 6% 𝑂2), uma maior emissão de 𝑁𝑂𝑥 nos ensaios com briquetes de podas de kiwi (1140 mg/𝑚3 @ 6% 𝑂2), no que diz respeito as emissões de partículas as podas de kiwi apresentam maior emissão (189 mg/𝑚3 @ 6% 𝑂2) e observa-se maior emissão de COT nas podas de oliveira (301 mg/𝑚3 @ 6% 𝑂2). Em suma, as podas mais adequadas são as podas de vinha, podas de oliveira, podas urbanas, podas de macieira e podas de kiwi. Por fim foi realizada uma Avaliação do Ciclo de Vida (ACV) simplificada de todo o processo que envolve a combustão de resíduos de biomassa na forma de briquetes, desde a etapa da poda até ao fim de vida de todo o processo. Portanto, foi desprezado o cultivo da biomassa neste estudo, assumindo já esse cultivo como realizado, dando apenas foco à poda da biomassa, bem como às restantes etapas. Nesta ACV foram considerados os recursos utilizados em cada etapa do processo, emissões resultantes e energia, com o intuito de compreender qual ou quais as etapas mais prejudiciais em todo o processo da atividade, o que veio a comprovar que a queima de resíduos de vinha ao ar livre é mais gravosa nas alterações climáticas (15 𝑘𝑔𝐶𝑂2𝑒𝑞), material particulado (6,5 PM2.5𝑒𝑞) e na formação fotoquímica de ozono (18 kg 𝑁𝑀𝑉𝑂𝐶𝑒𝑞), enquanto a combustão na caldeira do mesmo resíduo em forma de briquete apresenta agravantes na acidificação (19,2 moles de 𝐻𝑒𝑞) e na eutrofização (66 moles de 𝑁𝑒𝑞).
This dissertation was carried out within the scope of the Dissertation/Project/Internship Curricular Unit, which is part of the study plan of the Master Course in Sustainable Energies, lectured at Instituto Superior de Engenharia do Porto (ISEP). This work is part of a project to valorize biomass pruning through energy recovery, and was developed at the Centre for Waste Valorisation (CVR) in partnership with other Portuguese and Spanish research centers, to promote the energetic valorization of new biofuels. Forest and garden residues represent wood-cellulosic biomass sources with potential interest as raw material in the production of compacted Refuse Derived Fuel (FDRc), which can later be used to produce energy in boilers, or to produce biochar and bio-oil in pyrolysis systems. Combustion in boilers requires the use of certified CRDc and in accordance with legal requirements, in particular as regards moisture and ash content and calorific value. The presence of other contaminants is also heavily restricted in order to guarantee the emission limit values (VLE) of gaseous emissions. Thus, the study of viability in this type of waste recovery is relevant. The objectives of this work are specifically focused on the study of flue gas emissions from a boiler with several types of solid fuels. Commercial briquettes (pine) and briquettes from biomass pruning were used for this purpose, both briquettes were produced in the CVR using forest biomass residues such as pine sawdust, grapevine, kiwi, apple, olive and urban pruning’s. In order to achieve these objectives, the experimental installation which was set up, in addition to the boiler, included several components used in the measurements throughout the tests. In a first stage of the work, studies were performed on biomasses described above to obtain a knowledge about biomass characteristics. These studies were fulfilled to determine the moisture content, ash content, volatile matter, fixed carbon, calorific value and elemental analysis of the fuels under study. Then, the study proceeded with the production of briquettes that were used to perform the combustion in the boiler. A technical datasheet was created, to resume the characteristics (length, mass, density and section area) of each briquette type, allowing to analyze how different characteristics they have, depending on the raw material used. It should be noted that all the briquettes were produced in the briquette machine using the same protocol. The following step was to perform the valorization of residual biomass through combustion. In the first part of the tests, the solid fuel characterization, the fuel mass flow rate, temperatures, flowrate, density, among others, were evaluated considering near steady-state conditions. In the second stage, the composition of the flue gases (O2, CO2, N2 and H2O) was analyzed. Finally, the pollutant emissions resulting from the combustion gases (CO, NOx, particles and TOC) were monitored, with a higher emission of CO in the test where sawmill briquettes were used, and a higher emission of NOx, when the briquettes of kiwi pruning were used in the tests. In short, the most suitable pruning is vine pruning, olive pruning, urban pruning, apple pruning and kiwi pruning. Finally, a simplified life cycle assessment (LCA) of the entire process involving the combustion of biomass residues in the form of briquettes was performed, from the pruning stage to the end of life of the whole process. Cultivation was not accounted for in this report, giving only focus on biomass pruning, as well as the remaining stages. In this LCA, the resources used in each stage of the process, resulting emissions and energy consumed were taken into account, in order to understand what was the most harmful in the whole process of the activity, having been shown that the outdoor burning of vine wastes is the most harmful in what concerns the impact categories climate change, as well as particulate matter and the photochemical formation of ozone, while combustion in the boiler of the same briquette wastes shows aggravating factors in acidification and eutrophication.
This dissertation was carried out within the scope of the Dissertation/Project/Internship Curricular Unit, which is part of the study plan of the Master Course in Sustainable Energies, lectured at Instituto Superior de Engenharia do Porto (ISEP). This work is part of a project to valorize biomass pruning through energy recovery, and was developed at the Centre for Waste Valorisation (CVR) in partnership with other Portuguese and Spanish research centers, to promote the energetic valorization of new biofuels. Forest and garden residues represent wood-cellulosic biomass sources with potential interest as raw material in the production of compacted Refuse Derived Fuel (FDRc), which can later be used to produce energy in boilers, or to produce biochar and bio-oil in pyrolysis systems. Combustion in boilers requires the use of certified CRDc and in accordance with legal requirements, in particular as regards moisture and ash content and calorific value. The presence of other contaminants is also heavily restricted in order to guarantee the emission limit values (VLE) of gaseous emissions. Thus, the study of viability in this type of waste recovery is relevant. The objectives of this work are specifically focused on the study of flue gas emissions from a boiler with several types of solid fuels. Commercial briquettes (pine) and briquettes from biomass pruning were used for this purpose, both briquettes were produced in the CVR using forest biomass residues such as pine sawdust, grapevine, kiwi, apple, olive and urban pruning’s. In order to achieve these objectives, the experimental installation which was set up, in addition to the boiler, included several components used in the measurements throughout the tests. In a first stage of the work, studies were performed on biomasses described above to obtain a knowledge about biomass characteristics. These studies were fulfilled to determine the moisture content, ash content, volatile matter, fixed carbon, calorific value and elemental analysis of the fuels under study. Then, the study proceeded with the production of briquettes that were used to perform the combustion in the boiler. A technical datasheet was created, to resume the characteristics (length, mass, density and section area) of each briquette type, allowing to analyze how different characteristics they have, depending on the raw material used. It should be noted that all the briquettes were produced in the briquette machine using the same protocol. The following step was to perform the valorization of residual biomass through combustion. In the first part of the tests, the solid fuel characterization, the fuel mass flow rate, temperatures, flowrate, density, among others, were evaluated considering near steady-state conditions. In the second stage, the composition of the flue gases (O2, CO2, N2 and H2O) was analyzed. Finally, the pollutant emissions resulting from the combustion gases (CO, NOx, particles and TOC) were monitored, with a higher emission of CO in the test where sawmill briquettes were used, and a higher emission of NOx, when the briquettes of kiwi pruning were used in the tests. In short, the most suitable pruning is vine pruning, olive pruning, urban pruning, apple pruning and kiwi pruning. Finally, a simplified life cycle assessment (LCA) of the entire process involving the combustion of biomass residues in the form of briquettes was performed, from the pruning stage to the end of life of the whole process. Cultivation was not accounted for in this report, giving only focus on biomass pruning, as well as the remaining stages. In this LCA, the resources used in each stage of the process, resulting emissions and energy consumed were taken into account, in order to understand what was the most harmful in the whole process of the activity, having been shown that the outdoor burning of vine wastes is the most harmful in what concerns the impact categories climate change, as well as particulate matter and the photochemical formation of ozone, while combustion in the boiler of the same briquette wastes shows aggravating factors in acidification and eutrophication.
Description
Keywords
Avaliação de ciclo de vida Biocombustível sólido Biomassa residual Combustão Combustível derivado de resíduos compactado (CDRc) Emissões dos gases de combustão Podas de agricultura Poder calorífico superior Agriculture pruning Combustion Emissions of combustion gases Higher heating value Life cycle analysis Refuse derived fuel compacted (RDFc) Residual biomass Solid biofuel