Estudo do desempenho de carbonos ativados para a remoção de H2S do biogás

• Ano de defesa: 2017
• Autor(a) principal: Menezes, Randreanne Lybine da Costa Bandeira
• Orientador(a): Bastos Neto, Moisés
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Adsorção; Sulfeto de hidrogênio; Carbono ativado; Biogás; Engenharia química; Adsorption; Hydrogen sulfide; Activated carbons
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/22537

The use of biogas as a source of energy represents an alternative to the use of fossil fuels. However, this gas mixture presents contaminants in its composition, among them the hydrogen sulfide (H2S), which causes harmful effects to health and corrosion in equipment. Thus, the removal of H2S from the biogas is usually conducted by means of conventional absorption processes in amine solutions, which usually have a rather onerous regeneration step. In this context, the adsorption in porous materials, especially activated carbons, has been shown as an attractive alternative for the removal process. The objective of this work was to study the performance of three commercial activated carbons, one of them being the base matrix and the other impregnated with sodium hydroxide and iron oxide, for the removal of H2S in fixed bed. The adsorbents were characterized by X-ray fluorescence, pH measurement and removal of N2 isotherms at -196 °C and CO2 at 0 °C. From the characterization tests, it was observed that all the samples presented specific surface areas and high microporosity. In relation to H2S adsorption, the results showed that sodium impregnated carbon was the one with the highest H2S removal capacity due to its high alkalinity and percentage of ultramicropores, detected in the characterization. This suggests that the presence of the metals and the modification of the porous structure due to the impregnation process are the determinant factors to obtain a high capacity of H2S retention. The results for tests carried out at different temperatures showed that the dominant mechanism is for the impregnated samples. However, the regenerability study showed that the samples are not suitable for use in cyclic adsorption processes, since there is a significant loss of H2S adsorption capacity during the cycles. This loss is due to the mechanism involved, whereby H2S molecules form covalent bonds with the surface, making them more difficult to remove during regeneration. In spite of having a more moderate adsorption capacity, the matrix sample (not impregnated) maintained its capacity after the second cycle of use and regeneration, indicating predominance of physical adsorption mechanism and better potential for use in cyclic processes.