Thermal drying of biological sludge from paper mill for energy purposes

• Ano de defesa: 2017
• Autor(a) principal: Avelar, Nayara Vilela
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Biomassa; Biocombustíveis; Lodo; Fornalhas; Meios de transferência de calor; Engenharias
• Link de acesso: http://www.locus.ufv.br/handle/123456789/11184

This research proposes and investigates a drying system using hot gases from a direct coal-furnace as the energy source for biosludge drying, in order to transform it into a fuel for biomass boilers. The materials used were biosludge from a paper mill, and eucalyptus chips and bark as bulking agents. Two different proportions (15% and 25%) were applied. The thesis was divided into four chapters: Chapter I is a paper review that investigated the use of thermal sludge drying technologies for energy purposes. In Chapter II, the characteristics and thermal behavior of the materials and their mixtures were determined. In Chapter III, the drying system was evaluated according to its moisture reduction capacity, final total solids content, drying process efficiency and specific energy consumption. In Chapter IV, a simulation model for the biosludge drying process was implemented to predict the temperature and moisture distribution inside the biosludge, using the COMSOL Multiphysics® simulation program v5.2. The results showed that the addition of either eucalyptus chips or bark improved the biosludge physical and thermochemical characteristics. The proposed drying system was a promising technique when a bulking agent was added to the biosludge. The mixture of biosludge with 25% eucalyptus bark achieved the best drying results, increasing the total solids content from 31 to 72%, over a 5 hour drying interval. The simulation model was found to be an important tool to optimize the drying process and develop better strategies for the control of the system. It can be concluded that the results obtained are a significant step in the development of drying methods capable of using secondary energy (gases released from boilers), potentially available in industrial environments. The combustion of biosludge mixtures may provide an attractive option for the disposal and utilization of a renewable waste source such as industrial sludge.