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Optimization of hydrogen production with CO2 capture by autothermal chemical-looping reforming using different bioethanol purities

García-Díez, E., García-Labiano, F., de Diego, L.F., Abad, A., Gayán, P., Adánez, J., Ruíz, J.A.C.
Applied energy 2016 v.169 pp. 491-498
air, bioethanol, carbon dioxide, endothermy, energy, ethanol, greenhouse gas emissions, heat, hydrogen, hydrogen production, synthesis gas
Autothermal Chemical-Looping Reforming (a-CLR) is a process which allows hydrogen production avoiding the environmental penalty of CO2 emission typically produced in other processes. The major advantage of this technology is that the heat needed for syngas production is generated by the process itself. The heat necessary for the endothermic reactions is supplied by a Ni-based oxygen-carrier (OC) circulating between two reactors: the air reactor (AR), where the OC is oxidized by air, and the fuel reactor (FR), where the fuel is converted to syngas. Other important advantage is that this process also allows the production of pure N2 in the AR outlet stream. A renewable fuel such as bioethanol was chosen in this work due to their increasing worldwide production and the current excess of this fuel presented by different countries.In this work, mass and heat balances were done to determine the auto-thermal conditions that maximize H2 production, assuming that the product gas was in thermodynamic equilibrium. Three different types of bioethanol has been considered according to their ethanol purity; Dehydrated ethanol (≈100vol.%), hydrated ethanol (≈96vol.%), and diluted ethanol (≈52vol.%). It has been observed that the higher H2 production (4.62mol of H2 per mol of EtOH) has been obtained with the use of diluted ethanol and the surplus energy needed could be compensated by the energy save achieved during the purification of ethanol in the production process.