A comparative study on energetic and exergetic assessment of hydrogen production from bioethanol via steam reforming, partial oxidation and auto-thermal reforming processes

Three known types of ethanol reforming processes, ethanol steam reforming (ESR), partial oxidation (POX) and auto-thermal reforming (ATR), are investigated. Favorable operating conditions are identified for each reaction system to maximize the production of hydrogen from bioethanol. Each process consists of three sections: the main reactor (ESR, POX or ATR), the CO clean-up section comprised of the water gas shift reactor and preferential CO oxidation reactor and finally, the purification section. The performances of these processes are evaluated through mass, energy and exergy analyses.The material balances show that the total amount of ethanol required to generate 1 mol of hydrogen is 0.23 mol for the ATR, 0.24 mol for the POX and 0.25 mol for the ESR. The ATR reforming process is shown to have the highest energetic efficiency, i.e., the lowest amount of energy is consumed to produce the same amount of hydrogen from ethanol. Moreover, the ATR process has the best exergetic performance, as it presents the highest ratio of exergy recovered in the hydrogen stream to the total exergy supplied to the system. For all three of the systems, the exergy destruction occurs mainly in the reformer due to the high irreversibility of the reaction.

► Exergy and energy analyses are performed to compare bioethanol-to-hydrogen processes. ► Best insight in process efficiency is given by exergetic efficiency. ► Bioethanol auto-thermal reforming process has the best performances. ► Main part of the processes exergy destroyed occurs in the chemical reactors.