Development of a novel renewable energy-based integrated system coupling biomass and H2S sources for clean hydrogen production

The present work aims to develop a novel integrated energy system to produce clean hydrogen, power, and biochar. The Palmaria palmata, a type of seaweed, and hydrogen sulfide from the industrial gaseous waste streams are taken as potential feedstock. A combined thermochemical approach is employed for the processing of both feedstocks. For clean hydrogen production, the zinc sulfide thermochemical cycle is employed. Both stoichiometric and non-stoichiometric equilibrium-based models of the proposed plant design are developed in the Aspen Plus software, and a comprehensive thermodynamic analysis of the system is also performed by evaluating energy and exergy efficiencies. The study further explores and covers the modeling, simulation, and parametric analyses of various subsections to enhance the hydrogen and biochar production rate. The parametric analyses show that the first step of the thermochemical cycle (desulfurization reaction) follows a stoichiometric pathway and the optimal conversion is achieved at a ZnO/H2S ratio equal to 1. On the other hand, the second step of the thermochemical cycle (regeneration reaction) does not follow a stoichiometric pathway, and ZnS conversion of 12.87 % is achieved at a high temperature of 1400 °C. It is found that a hydrogen production rate of 0.71 mol/s is achieved with the introduction of 0.27 mol/s of H2S. The energy and exergy efficiencies of the zinc sulfide thermochemical cycle are found to be 65.23 % and 35.58 % respectively. A biochar production rate of 0.024 kg/s is obtained with the Palmaria palmata feed rate of 0.097 kg/s. The Palmaria to biochar energy and exergy efficiencies are found to be 55.43 % and 45.91 % respectively. The overall energy and exergy efficiencies of the proposed plant are determined to be 72.88 % and 50.03 % respectively.