Reforma a vapor de glicerol refinado em um reator de recuperação de calor de leito fixo: análise de exergia

Abstract

In the present work the exergy analysis of the refined glycerol steam reforming process was performed. The process was carried out in a fixed bed reactor, which recovered the heat from the exhaust gases of a diesel engine. Using the reforming experimental data, which were obtained by varying the glycerol mass concentration in the reactants from 10 to 90% and the outlet reactor temperature from 600 to 800 oC, the influence of these parameters over the thermodynamic imperfections inherent to the process could be investigated and quantified. The process achieved its maximum exergetic efficiency (69,5%) by injecting 70%wt of glycerol in the reactants with an outlet reactor temperature of 600 oC. This regime produced a synthesis gas with lower heat value of 16,7 MJ/kg. However, it is recommended for large scale application to maintain this glycerol concentration and increase the temperature to 700 oC, because, under these conditions, the reforming produced a synthesis gas with approximately twice the lower heat value (32,7 MJ/kg), with reduction of the exergetic efficiency of only 4%. It was noted as well that, for regimes with glycerol mass concentration up to 70%, the exergy losses through formation of undesired by-products were insignificant when compared to the losses due to the irreversibilities in the reactor, demonstrating that the reactor has a considerable potential for optimization. It was also observed that the irreversibilities are enhanced by increasing the water concentration in the reactants. Regimes with injection of 90%wt of glycerol turned up to be impractical by virtue of the high exergy losses due to the formation of tar and to the restrictions of the operational temperature of a heat recovery reactor. The results of this work indicate that the studied process, when correctly parameterized, has potential of industrial application comparable to other similar processes found in the literature.