Remoção de H2S e CO2 de biogás para utilização energética

• Autor(a) principal: Maia, Djeine Cristina Schiavon
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/3815
• topic: Purificação de biogás; Sulfeto de hidrogênio; Dióxido de carbono; Catalisador Fe/EDTA.; Biogas purification; Hydrogen sulfide; Carbon dioxide; Fe/edta catalyst.Fe/EDTA; Brazil.; Engenharias; Engenharia Química

Biogas is a product of microbiological degradation processes of organic matter. This gas consists mainly of methane, carbonic dioxide and small amounts of hydrogen, nitrogen and hydrogen sulfide. The high concentration of methane makes biogas an attractive fuel and its use solves an emission problem, since methane has a global warming effect 21 times superior than carbon dioxide. Although the hydrogen sulfide is present in small quantities, it is a highly toxic and corrosive gas, and it is one of the larger pollutants of the atmosphere. On the other hand, for energetic use, the carbon dioxide in the biogas can be considered inert, indicating the importance of removing the CO2 component in order to increase the calorific value of biogas. In this sense, this work was devoted to investigate the absorption efficiency of H2S into catalyst solutions of Fe/EDTA, in a synthetic biogas streams, as well as to investigate the physical absorption efficiency of CO2 into Fe/EDTA and then into water. Experimental studies were carried out with catalytic solutions of 0.2 and 0.4 mol/L of Fe/EDTA synthesized in laboratory. The H2S absorbed into this catalytic solution participates in a redox reaction. Therefore the sulfur element in the 2- oxidation state was converted to the insoluble state Sº, while the Fe3+ cation was reduced to Fe2+. The Sº, being water-insoluble, remained as a solid phase dispersed in solution. The spent Fe/EDTA solution was filtered to remove solid sulfur and then regenerated back to the Fe3+ form through oxygenation in a second bubbling column with air in counter-current with the solution. Furthermore, it was carried out experiments in order to evaluate the growth of sulfur particles formed in the removal of H2S from biogas with the Fe/EDTA solution, during ten hours of chemistry reaction, in a continuous system composed of an absorption column and a regeneration column. The particles size was determined by an Olympus - BX41 microscopic, coupled with a digital camera, using the particle counting software, Image Pro Plus 5.0. At the end of ten hours, it was observed the stabilization in the particles growth around an average diameter of 18 µm. From these results was projected a sedimentation vessel from the test tube experiments, by Talmadge and Fitch methodology. In chemical absorption in batch, without the regeneration state of the Fe/EDTA catalytic solution, 250 mL of this solution were used in different concentrations in the absorption column with the passage of 250 mL/min of biogas. The results of the H2S removal indicated that the concentration of the Fe/EDTA catalytic solution exerts strong influence on the catalytic activity. Considering the CO2 absorption in the Fe/EDTA solution and lately the absorption of this component into the absorption column with glass Raschig rings, with 1400 mL/min of water, it was possible to obtain a maximum CO2 absorption efficiency of 91.71% of initial biogas in the experimental unit, which represents an increase of approximately 15.83% in the biogas calorific power turning from 8.03 kWh/m3 to 9.30 kWh/m3. The results demonstrated that it is possible to totally remove the H2S from the biogas with the Fe/EDTA catalytic solution into steady state with the regeneration of the catalytic solution.