(263c) Modelling Hydrogen Production Via Combined Hydrothermal Liquefaction of Macroalgae Saccharina japonica and Hydrothermal Gasification of Aqueous Product Using Aspen Plus ®

Hydrothermal liquefaction (HTL) of biomass has attracted an immense attention as an economical route for energy production as compared to other conversion pathways. The depolymerization of the feedstock typically takes place at an operating condition of 250-400ËšC with a pressure of 4-20 MPa. HTL can treat wet feedstock, which reduces the cost for its pretreatment and drying, and hence making the conversion more economical in comparison to other processes. This study focuses on the combined hydrothermal liquefaction of Saccharina japonica to produce biocrude and hydrothermal gasification of aqueous product to produce hydrogen, which will be used as a feed for biocrude upgrading and other commercial purposes. Macroalgae feed of 140,000 lb/hr was fed to the HTL reactor at operating conditions of 300ËšC and 21 MPa. A balanced reactor was achieved yielding 76.5 wt.% liquid product, 8.59 wt.% of gas phase and 7.95 wt.% of non-soluble products. Hydrothermal liquefaction was simulated using a stoichiometric reactor model prior to which a mass balance between the feed analyses (Proximate, Ultimate, and Sulfanal analyses) and compounds in HTL products was developed. Phase separator separated the product in various phases (gas, aqueous, and organic phase). Gas phase product was processed via steam reforming followed by the water gas shift reaction and finally by pressure swing adsorption (PSA) for hydrogen production. Aqueous phase product was undergone hydrothermal gasification in a Gibbs reactor model, in which all the compounds were considered as products and were later served as a feed for the PSA Unit. PSA produces 4,252 kg/hr of hydrogen and of the off-gas consisting of CH₄, C₂H₆, CO, CO₂, N₂ and a minute fraction of H₂. The techno-economic study was performed to investigate the economic potential for the contribution of this process route towards the energy sector. Sensitivity analyses were also performed which helped in finding the optimal minimum selling price for the hydrogen.

Acknowledgment: This research was respectfully supported by Engineering Development Research Center (EDRC) funded by the Ministry of Trade, Industry & Energy (MOTIE). (No. N0000990)