Steam reforming for winery wastewater treatment: Hydrogen production and energy self-sufficiency assessment

A thermodynamic assessment using Gibbs free energy minimization to explore the potential of winery wastewater steam reforming (WWWSR) as a technique to treat water while simultaneously producing renewable hydrogen was conducted for the first time. This assessment focused on four types of reactors: a conventional reactor (CR), a sorption-enhanced reactor (SER) with CO2 capture, a membrane reactor (MR) with H2 removal, and a sorption-enhanced membrane reactor (SEMR) that combines features of both the SER and MR. The effects on WWWSR of temperature, pressure, water content in the feed, composition of winery wastewater (WWW), sorbent to feed ratio (SFR), and the split fraction of H2 in the membrane were studied. For the CR, SER, MR, and SEMR, the study showed that low pressures and high water content in the reactor inlet resulted in higher hydrogen production. Considering a representative WWW composition with a water content of 75 wt% in the feed, it was shown that the CR needed to operate at extremely high temperatures (over 600 degrees C) to maximize H2 yield while producing less hydrogen than its counterparts. In contrast, the MR and SER achieved higher hydrogen production at optimal temperatures around 500 degrees C, while the SEMR performed even better, producing more hydrogen at just 400 degrees C. Moreover, the organic composition of the feed stream did not significantly influence the optimal temperature and pressure conditions for maximizing hydrogen production. However, wastewater with a higher fraction of sugars generated more hydrogen, whereas wastewater with a higher fraction of acetic acid produced less hydrogen via the steam reforming reaction. Notably, a novel energy analysis was conducted, demonstrating that the energy self-sufficiency of this process changed drastically when different reactor types were considered. Only the MR with a high degree of hydrogen separation in the membrane, the SER with optimal quantities of CO2-capturing sorbent, and the SEMR can be energetically selfsufficient, as they produce enough hydrogen to offset the energy expenditure associated with steam reforming.